Backup fail with ExtraUnknownFiles

Support
1

the last couple weeks my scheduled daily backups fail with ExtraRemoteFiles. to correct the failure i have Repair and also Recreate (delete and repair) the database several times. my configuration is WebDAV to a Nextcloud instance. this morning i ran Repair, verified via rclone there were no .part files, ran manual Start and collected this log.

{
  "DeletedFiles": 9043,
  "DeletedFolders": 1472,
  "ModifiedFiles": 120,
  "ExaminedFiles": 406225,
  "OpenedFiles": 461,
  "AddedFiles": 341,
  "SizeOfModifiedFiles": 7223015189,
  "SizeOfAddedFiles": 267782378,
  "SizeOfExaminedFiles": 77437180533,
  "SizeOfOpenedFiles": 7490985824,
  "NotProcessedFiles": 0,
  "AddedFolders": 22,
  "TooLargeFiles": 0,
  "FilesWithError": 0,
  "TimestampChangedFiles": 0,
  "ModifiedFolders": 52,
  "ModifiedSymlinks": 0,
  "AddedSymlinks": 0,
  "DeletedSymlinks": 0,
  "PartialBackup": false,
  "Dryrun": false,
  "MainOperation": "Backup",
  "CompactResults": {
    "DeletedFileCount": 10,
    "DownloadedFileCount": 0,
    "UploadedFileCount": 0,
    "DeletedFileSize": 259361602,
    "DownloadedFileSize": 0,
    "UploadedFileSize": 0,
    "Dryrun": false,
    "VacuumResults": null,
    "MainOperation": "Compact",
    "ParsedResult": "Success",
    "Interrupted": false,
    "Version": "2.2.0.2 (2.2.0.2_beta_2025-11-26)",
    "EndTime": "2025-12-08T12:50:47.6518101Z",
    "BeginTime": "2025-12-08T12:50:19.9989389Z",
    "Duration": "00:00:27.6528712",
    "MessagesActualLength": 0,
    "WarningsActualLength": 0,
    "ErrorsActualLength": 0,
    "Messages": null,
    "Warnings": null,
    "Errors": null,
    "BackendStatistics": {
      "RemoteCalls": 63,
      "BytesUploaded": 1170562755,
      "BytesDownloaded": 0,
      "FilesUploaded": 47,
      "FilesDownloaded": 0,
      "FilesDeleted": 11,
      "FoldersCreated": 0,
      "RetryAttempts": 3,
      "UnknownFileSize": 0,
      "UnknownFileCount": 0,
      "KnownFileCount": 8094,
      "KnownFileSize": 208173429391,
      "KnownFilesets": 23,
      "LastBackupDate": "2025-12-08T07:37:46-05:00",
      "BackupListCount": 23,
      "TotalQuotaSpace": 0,
      "FreeQuotaSpace": 0,
      "AssignedQuotaSpace": -1,
      "ReportedQuotaError": false,
      "ReportedQuotaWarning": false,
      "MainOperation": "Backup",
      "ParsedResult": "Success",
      "Interrupted": false,
      "Version": "2.2.0.2 (2.2.0.2_beta_2025-11-26)",
      "EndTime": "0001-01-01T00:00:00",
      "BeginTime": "2025-12-08T12:37:46.6362523Z",
      "Duration": "00:00:00",
      "MessagesActualLength": 0,
      "WarningsActualLength": 0,
      "ErrorsActualLength": 0,
      "Messages": null,
      "Warnings": null,
      "Errors": null
    }
  },
  "VacuumResults": null,
  "DeleteResults": {
    "DeletedSetsActualLength": 1,
    "DeletedSets": [
      {
        "Item1": 1,
        "Item2": "2025-12-08T06:13:11-05:00"
      }
    ],
    "Dryrun": false,
    "MainOperation": "Delete",
    "CompactResults": {
      "DeletedFileCount": 10,
      "DownloadedFileCount": 0,
      "UploadedFileCount": 0,
      "DeletedFileSize": 259361602,
      "DownloadedFileSize": 0,
      "UploadedFileSize": 0,
      "Dryrun": false,
      "VacuumResults": null,
      "MainOperation": "Compact",
      "ParsedResult": "Success",
      "Interrupted": false,
      "Version": "2.2.0.2 (2.2.0.2_beta_2025-11-26)",
      "EndTime": "2025-12-08T12:50:47.6518101Z",
      "BeginTime": "2025-12-08T12:50:19.9989389Z",
      "Duration": "00:00:27.6528712",
      "MessagesActualLength": 0,
      "WarningsActualLength": 0,
      "ErrorsActualLength": 0,
      "Messages": null,
      "Warnings": null,
      "Errors": null,
      "BackendStatistics": {
        "RemoteCalls": 63,
        "BytesUploaded": 1170562755,
        "BytesDownloaded": 0,
        "FilesUploaded": 47,
        "FilesDownloaded": 0,
        "FilesDeleted": 11,
        "FoldersCreated": 0,
        "RetryAttempts": 3,
        "UnknownFileSize": 0,
        "UnknownFileCount": 0,
        "KnownFileCount": 8094,
        "KnownFileSize": 208173429391,
        "KnownFilesets": 23,
        "LastBackupDate": "2025-12-08T07:37:46-05:00",
        "BackupListCount": 23,
        "TotalQuotaSpace": 0,
        "FreeQuotaSpace": 0,
        "AssignedQuotaSpace": -1,
        "ReportedQuotaError": false,
        "ReportedQuotaWarning": false,
        "MainOperation": "Backup",
        "ParsedResult": "Success",
        "Interrupted": false,
        "Version": "2.2.0.2 (2.2.0.2_beta_2025-11-26)",
        "EndTime": "0001-01-01T00:00:00",
        "BeginTime": "2025-12-08T12:37:46.6362523Z",
        "Duration": "00:00:00",
        "MessagesActualLength": 0,
        "WarningsActualLength": 0,
        "ErrorsActualLength": 0,
        "Messages": null,
        "Warnings": null,
        "Errors": null
      }
    },
    "ParsedResult": "Success",
    "Interrupted": false,
    "Version": "2.2.0.2 (2.2.0.2_beta_2025-11-26)",
    "EndTime": "2025-12-08T12:50:47.6518556Z",
    "BeginTime": "2025-12-08T12:49:57.3020783Z",
    "Duration": "00:00:50.3497773",
    "MessagesActualLength": 0,
    "WarningsActualLength": 0,
    "ErrorsActualLength": 0,
    "Messages": null,
    "Warnings": null,
    "Errors": null,
    "BackendStatistics": {
      "RemoteCalls": 63,
      "BytesUploaded": 1170562755,
      "BytesDownloaded": 0,
      "FilesUploaded": 47,
      "FilesDownloaded": 0,
      "FilesDeleted": 11,
      "FoldersCreated": 0,
      "RetryAttempts": 3,
      "UnknownFileSize": 0,
      "UnknownFileCount": 0,
      "KnownFileCount": 8094,
      "KnownFileSize": 208173429391,
      "KnownFilesets": 23,
      "LastBackupDate": "2025-12-08T07:37:46-05:00",
      "BackupListCount": 23,
      "TotalQuotaSpace": 0,
      "FreeQuotaSpace": 0,
      "AssignedQuotaSpace": -1,
      "ReportedQuotaError": false,
      "ReportedQuotaWarning": false,
      "MainOperation": "Backup",
      "ParsedResult": "Success",
      "Interrupted": false,
      "Version": "2.2.0.2 (2.2.0.2_beta_2025-11-26)",
      "EndTime": "0001-01-01T00:00:00",
      "BeginTime": "2025-12-08T12:37:46.6362523Z",
      "Duration": "00:00:00",
      "MessagesActualLength": 0,
      "WarningsActualLength": 0,
      "ErrorsActualLength": 0,
      "Messages": null,
      "Warnings": null,
      "Errors": null
    }
  },
  "RepairResults": null,
  "TestResults": null,
  "ParsedResult": "Fatal",
  "Interrupted": false,
  "Version": "2.2.0.2 (2.2.0.2_beta_2025-11-26)",
  "EndTime": "2025-12-08T12:50:50.2934375Z",
  "BeginTime": "2025-12-08T12:37:46.636249Z",
  "Duration": "00:13:03.6571885",
  "MessagesActualLength": 150,
  "WarningsActualLength": 3,
  "ErrorsActualLength": 3,
  "Messages": [
    "2025-12-08 07:37:46 -05 - [Information-Duplicati.Library.Main.Controller-StartingOperation]: The operation Backup has started",
    "2025-12-08 07:39:04 -05 - [Information-Duplicati.Library.Main.BasicResults-BackendEvent]: Backend event: List - Started:  ()",
    "2025-12-08 07:39:05 -05 - [Information-Duplicati.Library.Main.BasicResults-BackendEvent]: Backend event: List - Completed:  (7.866 KiB)",
    "2025-12-08 07:40:55 -05 - [Information-Duplicati.Library.Main.BasicResults-BackendEvent]: Backend event: Put - Started: duplicati-b8670bbd0df934d7e97ef7d827b061e1e.dblock.zip.aes (49.053 MiB)",
    "2025-12-08 07:40:55 -05 - [Information-Duplicati.Library.Main.BasicResults-BackendEvent]: Backend event: Put - Started: duplicati-bf4f76aba72ca44b8913c28e5013d99e2.dblock.zip.aes (49.109 MiB)",
    "2025-12-08 07:40:56 -05 - [Information-Duplicati.Library.Main.BasicResults-BackendEvent]: Backend event: Put - Started: duplicati-b1c32b053b9a244dfb112c4098dc43cb2.dblock.zip.aes (49.301 MiB)",
    "2025-12-08 07:40:57 -05 - [Information-Duplicati.Library.Main.BasicResults-BackendEvent]: Backend event: Put - Started: duplicati-b4679b4b49f9244f8a2cf292fefd7bf2f.dblock.zip.aes (49.441 MiB)",
    "2025-12-08 07:42:06 -05 - [Information-Duplicati.Library.Main.BasicResults-BackendEvent]: Backend event: Put - Completed: duplicati-b8670bbd0df934d7e97ef7d827b061e1e.dblock.zip.aes (49.053 MiB)",
    "2025-12-08 07:42:06 -05 - [Information-Duplicati.Library.Main.BasicResults-BackendEvent]: Backend event: Put - Started: duplicati-i13f0af64a3f94b9c9a4998b9e17298b1.dindex.zip.aes (8.138 KiB)",
    "2025-12-08 07:42:07 -05 - [Information-Duplicati.Library.Main.BasicResults-BackendEvent]: Backend event: Put - Completed: duplicati-i13f0af64a3f94b9c9a4998b9e17298b1.dindex.zip.aes (8.138 KiB)",
    "2025-12-08 07:42:07 -05 - [Information-Duplicati.Library.Main.BasicResults-BackendEvent]: Backend event: Put - Started: duplicati-b8d9766949bfa44cda18a967dc3c23444.dblock.zip.aes (49.349 MiB)",
    "2025-12-08 07:42:07 -05 - [Information-Duplicati.Library.Main.BasicResults-BackendEvent]: Backend event: Put - Completed: duplicati-bf4f76aba72ca44b8913c28e5013d99e2.dblock.zip.aes (49.109 MiB)",
    "2025-12-08 07:42:07 -05 - [Information-Duplicati.Library.Main.BasicResults-BackendEvent]: Backend event: Put - Started: duplicati-if68926ab65904de6b7789e3202fe1005.dindex.zip.aes (8.653 KiB)",
    "2025-12-08 07:42:10 -05 - [Information-Duplicati.Library.Main.BasicResults-BackendEvent]: Backend event: Put - Completed: duplicati-if68926ab65904de6b7789e3202fe1005.dindex.zip.aes (8.653 KiB)",
    "2025-12-08 07:42:10 -05 - [Information-Duplicati.Library.Main.BasicResults-BackendEvent]: Backend event: Put - Started: duplicati-bf025412e3a164111970498be2e8f6415.dblock.zip.aes (49.061 MiB)",
    "2025-12-08 07:42:13 -05 - [Information-Duplicati.Library.Main.BasicResults-BackendEvent]: Backend event: Put - Completed: duplicati-b1c32b053b9a244dfb112c4098dc43cb2.dblock.zip.aes (49.301 MiB)",
    "2025-12-08 07:42:13 -05 - [Information-Duplicati.Library.Main.BasicResults-BackendEvent]: Backend event: Put - Started: duplicati-i137aa32d60db4ae6b9ff055ec738a6e2.dindex.zip.aes (8.825 KiB)",
    "2025-12-08 07:42:13 -05 - [Information-Duplicati.Library.Main.BasicResults-BackendEvent]: Backend event: Put - Completed: duplicati-i137aa32d60db4ae6b9ff055ec738a6e2.dindex.zip.aes (8.825 KiB)",
    "2025-12-08 07:42:13 -05 - [Information-Duplicati.Library.Main.BasicResults-BackendEvent]: Backend event: Put - Started: duplicati-b0c55e2d97a6840438da7b12d2135cd8a.dblock.zip.aes (49.384 MiB)",
    "2025-12-08 07:42:15 -05 - [Information-Duplicati.Library.Main.BasicResults-BackendEvent]: Backend event: Put - Completed: duplicati-b4679b4b49f9244f8a2cf292fefd7bf2f.dblock.zip.aes (49.441 MiB)"
  ],
  "Warnings": [
    "2025-12-08 07:50:50 -05 - [Warning-Duplicati.Library.Main.Operation.FilelistProcessor-ExtraUnknownFile]: Extra unknown file: duplicati-b0c55e2d97a6840438da7b12d2135cd8a.dblock.zip.aes.part",
    "2025-12-08 07:50:50 -05 - [Warning-Duplicati.Library.Main.Operation.FilelistProcessor-ExtraUnknownFile]: Extra unknown file: duplicati-b2d2f6febeca348beb3f91d7c9dc75eee.dblock.zip.aes.part",
    "2025-12-08 07:50:50 -05 - [Warning-Duplicati.Library.Main.Operation.FilelistProcessor-ExtraUnknownFile]: Extra unknown file: duplicati-b6ccbaf992f4647299e014f47703e7709.dblock.zip.aes.part"
  ],
  "Errors": [
    "2025-12-08 07:50:50 -05 - [Error-Duplicati.Library.Main.Operation.FilelistProcessor-ExtraRemoteFiles]: Found 3 remote files that are not recorded in local storage. This can be caused by having two backups sharing a destination folder which is not supported. It can also be caused by restoring an old database. If you are certain that only one backup uses the folder and you have the most updated version of the database, you can use repair to delete the unknown files.",
    "2025-12-08 07:50:50 -05 - [Error-Duplicati.Library.Main.Operation.BackupHandler-FatalError]: Fatal error\nRemoteListVerificationException: Found 3 remote files that are not recorded in local storage. This can be caused by having two backups sharing a destination folder which is not supported. It can also be caused by restoring an old database. If you are certain that only one backup uses the folder and you have the most updated version of the database, you can use repair to delete the unknown files.",
    "2025-12-08 07:50:50 -05 - [Error-Duplicati.Library.Main.Controller-FailedOperation]: The operation Backup has failed\nRemoteListVerificationException: Found 3 remote files that are not recorded in local storage. This can be caused by having two backups sharing a destination folder which is not supported. It can also be caused by restoring an old database. If you are certain that only one backup uses the folder and you have the most updated version of the database, you can use repair to delete the unknown files."
  ],
  "BackendStatistics": {
    "RemoteCalls": 63,
    "BytesUploaded": 1170562755,
    "BytesDownloaded": 0,
    "FilesUploaded": 47,
    "FilesDownloaded": 0,
    "FilesDeleted": 11,
    "FoldersCreated": 0,
    "RetryAttempts": 3,
    "UnknownFileSize": 0,
    "UnknownFileCount": 0,
    "KnownFileCount": 8094,
    "KnownFileSize": 208173429391,
    "KnownFilesets": 23,
    "LastBackupDate": "2025-12-08T07:37:46-05:00",
    "BackupListCount": 23,
    "TotalQuotaSpace": 0,
    "FreeQuotaSpace": 0,
    "AssignedQuotaSpace": -1,
    "ReportedQuotaError": false,
    "ReportedQuotaWarning": false,
    "MainOperation": "Backup",
    "ParsedResult": "Success",
    "Interrupted": false,
    "Version": "2.2.0.2 (2.2.0.2_beta_2025-11-26)",
    "EndTime": "0001-01-01T00:00:00",
    "BeginTime": "2025-12-08T12:37:46.6362523Z",
    "Duration": "00:00:00",
    "MessagesActualLength": 0,
    "WarningsActualLength": 0,
    "ErrorsActualLength": 0,
    "Messages": null,
    "Warnings": null,
    "Errors": null
  }
}
Repeated error about "1 remote files that are not recorded in local storage."
2

i find it interesting there are 10 Started, 7 Completed and 3 ExtraUnknownFiles.

3

the failures occur with duplicati-2.2.0.1_stable_2025-11-09-linux-x64-gui.deb and duplicati-2.2.0.2_beta_2025-11-26-linux-x64-gui.deb on Kubuntu 24.04. i don’t remember offhand which version was last successful.

4

Welcome to the forum @jkt

means you saw 20 out of 150 lines, so it’s interesting, but not really conclusive.
It gets more interesting at the end and in next section, with one specific file and

“2025-12-08 07:42:13 -05 - [Information-Duplicati.Library.Main.BasicResults-BackendEvent]: Backend event: Put - Started: duplicati-b0c55e2d97a6840438da7b12d2135cd8a.dblock.zip.aes (49.384 MiB)”,

“2025-12-08 07:50:50 -05 - [Warning-Duplicati.Library.Main.Operation.FilelistProcessor-ExtraUnknownFile]: Extra unknown file: duplicati-b0c55e2d97a6840438da7b12d2135cd8a.dblock.zip.aes.part”,

The best explanation I could quickly find was Google AI Overview for the query:

nextcloud webdav "part file"

which says it could be from an upload failure. Duplicati retries these and counts.

So if you had set the advanced options log-file=<path> and log-file-log-level=retry you might have been able to see this more clearly, with all action.

Failed upload is retried with a new name, then name of failed upload is deleted.
Problem is that Duplicati won’t delete unexpected related Nextcloud .part file.

Is this local WebDAV? I can see how remote is more likely to get failed uploads.
Logging or similar in Nextcloud might also provide a view of any transfer issues.

Warning & Error: Extra unknown file, remote file not recorded in local storage
is what might be (awaiting your research) the equivalent problem but using FTP.

5

Nextcloud, thus WebDAV, is remote. thank you for the log-file suggestion; i’ve now enabled and started a new manual backup.

6

Any known changes to anything? You could also look at old job logs (although the default retention is only 30 days) to see if the extra file count matches retry count.

part_file_in_storage changed to false might be another option, although there is possible space usage concern there. I’m not sure why these files are kept around.

Automatically clean-up leftover .part files after failed uploads to shared folders #26179 and a related linked issue are still open. I didn’t research this very much…

7

as far as i remember, only duplicati. i’ve had this backup configuration running at least a year with little bother.

logs seem to go back only to last Recreate, which was yesterday.

is this a Nextcloud server setting? i checked the Administration panel and it seems my service provider does not provide a mechanism to change this.

8

Click link for context. I don’t use Nextcloud.

9

The logs are in the job database. I know you did Repair. I missed Recreate.
I wouldn’t expect Recreate to help though, in terms of deleting .part files.
There’s also a Nextcloud forum where maybe someone can provide advice.

This path is of course based on a theory of causation that’s not fully proven.
Maybe a failure will occur and you’ll see if new .part is from failed upload.
Besides the name Duplicati makes, you should have log time to the second.

10

i ran a manual backup with log-file enabled then traced the life of one extra unknown file:

2025-12-08 12:47:50 -05 - [Information-Duplicati.Library.Main.BasicResults-BackendEvent]: Backend event: Put - Started: duplicati-b2b345574247d4b6997a41ee5c123becd.dblock.zip.aes (49.910 MiB)
2025-12-08 12:49:07 -05 - [Retry-Duplicati.Library.Main.Backend.Handler-RetryPut]: Operation Put with file duplicati-b2b345574247d4b6997a41ee5c123becd.dblock.zip.aes attempt 1 of 5 failed with message: Response status code does not indicate success: 502 (Bad Gateway).
2025-12-08 12:49:07 -05 - [Information-Duplicati.Library.Main.BasicResults-BackendEvent]: Backend event: Put - Retrying: duplicati-b2b345574247d4b6997a41ee5c123becd.dblock.zip.aes ()
2025-12-08 12:49:17 -05 - [Information-Duplicati.Library.Main.BasicResults-BackendEvent]: Backend event: Put - Rename: duplicati-b2b345574247d4b6997a41ee5c123becd.dblock.zip.aes (49.910 MiB)
2025-12-08 12:49:17 -05 - [Information-Duplicati.Library.Main.BasicResults-BackendEvent]: Backend event: Put - Rename: duplicati-b7ec7366d7d214d1ab33c6521405b74fd.dblock.zip.aes (49.910 MiB)
2025-12-08 12:49:17 -05 - [Information-Duplicati.Library.Main.Backend.PutOperation-RenameRemoteTargetFile]: Renaming "duplicati-b2b345574247d4b6997a41ee5c123becd.dblock.zip.aes" to "duplicati-b7ec7366d7d214d1ab33c6521405b74fd.dblock.zip.aes"
2025-12-08 12:49:17 -05 - [Information-Duplicati.Library.Main.BasicResults-BackendEvent]: Backend event: Put - Started: duplicati-b7ec7366d7d214d1ab33c6521405b74fd.dblock.zip.aes (49.910 MiB)
2025-12-08 12:50:36 -05 - [Retry-Duplicati.Library.Main.Backend.Handler-RetryPut]: Operation Put with file duplicati-b7ec7366d7d214d1ab33c6521405b74fd.dblock.zip.aes attempt 2 of 5 failed with message: Response status code does not indicate success: 502 (Bad Gateway).
2025-12-08 12:50:36 -05 - [Information-Duplicati.Library.Main.BasicResults-BackendEvent]: Backend event: Put - Retrying: duplicati-b7ec7366d7d214d1ab33c6521405b74fd.dblock.zip.aes ()
2025-12-08 12:50:46 -05 - [Information-Duplicati.Library.Main.BasicResults-BackendEvent]: Backend event: Put - Rename: duplicati-b7ec7366d7d214d1ab33c6521405b74fd.dblock.zip.aes (49.910 MiB)
2025-12-08 12:50:46 -05 - [Information-Duplicati.Library.Main.Backend.PutOperation-RenameRemoteTargetFile]: Renaming "duplicati-b7ec7366d7d214d1ab33c6521405b74fd.dblock.zip.aes" to "duplicati-b36b4125cf66e4d409222a8ac329b0111.dblock.zip.aes"
2025-12-08 13:12:54 -05 - [Information-Duplicati.Library.Main.Operation.FilelistProcessor-RemoteUnwantedMissingFile]: Removing file listed as Deleting: duplicati-b2b345574247d4b6997a41ee5c123becd.dblock.zip.aes
2025-12-08 13:12:54 -05 - [Information-Duplicati.Library.Main.Operation.FilelistProcessor-RemoveUnwantedRemoteFile]: Removing remote file listed as Deleting: duplicati-b7ec7366d7d214d1ab33c6521405b74fd.dblock.zip.aes
2025-12-08 13:12:54 -05 - [Information-Duplicati.Library.Main.BasicResults-BackendEvent]: Backend event: Delete - Started: duplicati-b7ec7366d7d214d1ab33c6521405b74fd.dblock.zip.aes ()
2025-12-08 13:12:55 -05 - [Information-Duplicati.Library.Main.BasicResults-BackendEvent]: Backend event: Delete - Completed: duplicati-b7ec7366d7d214d1ab33c6521405b74fd.dblock.zip.aes ()
2025-12-08 13:12:57 -05 - [Warning-Duplicati.Library.Main.Operation.FilelistProcessor-ExtraUnknownFile]: Extra unknown file: duplicati-b2b345574247d4b6997a41ee5c123becd.dblock.zip.aes.part
jkt@ledgy:~/Nextcloud/tmp$ grep -E 'b2b345574247d4b6997a41ee5c123becd|b7ec7366d7d214d1ab33c6521405b74fd|b36b4125cf66e4d409222a8ac329b0111' duplicati-2025-12-08.log 
2025-12-08 12:47:50 -05 - [Information-Duplicati.Library.Main.BasicResults-BackendEvent]: Backend event: Put - Started: duplicati-b2b345574247d4b6997a41ee5c123becd.dblock.zip.aes (49.910 MiB)
2025-12-08 12:49:07 -05 - [Retry-Duplicati.Library.Main.Backend.Handler-RetryPut]: Operation Put with file duplicati-b2b345574247d4b6997a41ee5c123becd.dblock.zip.aes attempt 1 of 5 failed with message: Response status code does not indicate success: 502 (Bad Gateway).
2025-12-08 12:49:07 -05 - [Information-Duplicati.Library.Main.BasicResults-BackendEvent]: Backend event: Put - Retrying: duplicati-b2b345574247d4b6997a41ee5c123becd.dblock.zip.aes ()
2025-12-08 12:49:17 -05 - [Information-Duplicati.Library.Main.BasicResults-BackendEvent]: Backend event: Put - Rename: duplicati-b2b345574247d4b6997a41ee5c123becd.dblock.zip.aes (49.910 MiB)
2025-12-08 12:49:17 -05 - [Information-Duplicati.Library.Main.BasicResults-BackendEvent]: Backend event: Put - Rename: duplicati-b7ec7366d7d214d1ab33c6521405b74fd.dblock.zip.aes (49.910 MiB)
2025-12-08 12:49:17 -05 - [Information-Duplicati.Library.Main.Backend.PutOperation-RenameRemoteTargetFile]: Renaming "duplicati-b2b345574247d4b6997a41ee5c123becd.dblock.zip.aes" to "duplicati-b7ec7366d7d214d1ab33c6521405b74fd.dblock.zip.aes"
2025-12-08 12:49:17 -05 - [Information-Duplicati.Library.Main.BasicResults-BackendEvent]: Backend event: Put - Started: duplicati-b7ec7366d7d214d1ab33c6521405b74fd.dblock.zip.aes (49.910 MiB)
2025-12-08 12:50:36 -05 - [Retry-Duplicati.Library.Main.Backend.Handler-RetryPut]: Operation Put with file duplicati-b7ec7366d7d214d1ab33c6521405b74fd.dblock.zip.aes attempt 2 of 5 failed with message: Response status code does not indicate success: 502 (Bad Gateway).
2025-12-08 12:50:36 -05 - [Information-Duplicati.Library.Main.BasicResults-BackendEvent]: Backend event: Put - Retrying: duplicati-b7ec7366d7d214d1ab33c6521405b74fd.dblock.zip.aes ()
2025-12-08 12:50:46 -05 - [Information-Duplicati.Library.Main.BasicResults-BackendEvent]: Backend event: Put - Rename: duplicati-b7ec7366d7d214d1ab33c6521405b74fd.dblock.zip.aes (49.910 MiB)
2025-12-08 12:50:46 -05 - [Information-Duplicati.Library.Main.BasicResults-BackendEvent]: Backend event: Put - Rename: duplicati-b36b4125cf66e4d409222a8ac329b0111.dblock.zip.aes (49.910 MiB)
2025-12-08 12:50:46 -05 - [Information-Duplicati.Library.Main.Backend.PutOperation-RenameRemoteTargetFile]: Renaming "duplicati-b7ec7366d7d214d1ab33c6521405b74fd.dblock.zip.aes" to "duplicati-b36b4125cf66e4d409222a8ac329b0111.dblock.zip.aes"
2025-12-08 12:50:46 -05 - [Information-Duplicati.Library.Main.BasicResults-BackendEvent]: Backend event: Put - Started: duplicati-b36b4125cf66e4d409222a8ac329b0111.dblock.zip.aes (49.910 MiB)
2025-12-08 12:51:07 -05 - [Information-Duplicati.Library.Main.BasicResults-BackendEvent]: Backend event: Put - Completed: duplicati-b36b4125cf66e4d409222a8ac329b0111.dblock.zip.aes (49.910 MiB)
2025-12-08 13:12:54 -05 - [Information-Duplicati.Library.Main.Operation.FilelistProcessor-RemoteUnwantedMissingFile]: Removing file listed as Deleting: duplicati-b2b345574247d4b6997a41ee5c123becd.dblock.zip.aes
2025-12-08 13:12:54 -05 - [Information-Duplicati.Library.Main.Operation.FilelistProcessor-RemoveUnwantedRemoteFile]: Removing remote file listed as Deleting: duplicati-b7ec7366d7d214d1ab33c6521405b74fd.dblock.zip.aes
2025-12-08 13:12:54 -05 - [Information-Duplicati.Library.Main.BasicResults-BackendEvent]: Backend event: Delete - Started: duplicati-b7ec7366d7d214d1ab33c6521405b74fd.dblock.zip.aes ()
2025-12-08 13:12:55 -05 - [Information-Duplicati.Library.Main.BasicResults-BackendEvent]: Backend event: Delete - Completed: duplicati-b7ec7366d7d214d1ab33c6521405b74fd.dblock.zip.aes ()
2025-12-08 13:12:57 -05 - [Warning-Duplicati.Library.Main.Operation.FilelistProcessor-ExtraUnknownFile]: Extra unknown file: duplicati-b2b345574247d4b6997a41ee5c123becd.dblock.zip.aes.part

i think renaming an incomplete remote file will have wildly varied results depending on the backend. it certainly seems to create all manner of confusion with WebDAV / Nextcloud.

perhaps someone familiar with the order of operation can chime in whether previous versions executed Rename only after Put - Completed and at which version this changed.

i put the full log at duplicati-2025-12-08.log - Nextcloud.

11

There’s no renaming of old file in the traditional sense AFAIK. Source code here.

combined with your service provider choosing to leave them around to trip over.
Log doesn’t always get this, e.g. b7ec7366d7d214d1ab33c6521405b74fd didn’t.

Here is an analysis of the full log file starting with error and looking at its source:

Search Extra
2025-12-08 13:12:57 -05 - [Warning-Duplicati.Library.Main.Operation.FilelistProcessor-ExtraUnknownFile]: Extra unknown file: duplicati-b2b345574247d4b6997a41ee5c123becd.dblock.zip.aes.part
2025-12-08 13:12:57 -05 - [Warning-Duplicati.Library.Main.Operation.FilelistProcessor-ExtraUnknownFile]: Extra unknown file: duplicati-b3f52cad89a0d44e69c25c72002584467.dblock.zip.aes.part
2025-12-08 13:12:57 -05 - [Warning-Duplicati.Library.Main.Operation.FilelistProcessor-ExtraUnknownFile]: Extra unknown file: duplicati-bb67f648a3ec449b3978d8da44e60a346.dblock.zip.aes.part
2025-12-08 13:12:57 -05 - [Error-Duplicati.Library.Main.Operation.FilelistProcessor-ExtraRemoteFiles]: Found 3 remote files that are not recorded in local storage. This can be caused by having two backups sharing a destination folder which is not supported. It can also be caused by restoring an old database. If you are certain that only one backup uses the folder and you have the most updated version of the database, you can use repair to delete the unknown files.

Search b2b345574247d4b6997a41ee5c123becd|b3f52cad89a0d44e69c25c72002584467|bb67f648a3ec449b3978d8da44e60a346
2025-12-08 12:47:50 -05 - [Information-Duplicati.Library.Main.BasicResults-BackendEvent]: Backend event: Put - Started: duplicati-b2b345574247d4b6997a41ee5c123becd.dblock.zip.aes (49.910 MiB)
2025-12-08 12:49:07 -05 - [Retry-Duplicati.Library.Main.Backend.Handler-RetryPut]: Operation Put with file duplicati-b2b345574247d4b6997a41ee5c123becd.dblock.zip.aes attempt 1 of 5 failed with message: Response status code does not indicate success: 502 (Bad Gateway).
2025-12-08 12:49:07 -05 - [Information-Duplicati.Library.Main.BasicResults-BackendEvent]: Backend event: Put - Retrying: duplicati-b2b345574247d4b6997a41ee5c123becd.dblock.zip.aes ()
2025-12-08 12:49:17 -05 - [Information-Duplicati.Library.Main.BasicResults-BackendEvent]: Backend event: Put - Rename: duplicati-b2b345574247d4b6997a41ee5c123becd.dblock.zip.aes (49.910 MiB)
2025-12-08 12:49:17 -05 - [Information-Duplicati.Library.Main.Backend.PutOperation-RenameRemoteTargetFile]: Renaming "duplicati-b2b345574247d4b6997a41ee5c123becd.dblock.zip.aes" to "duplicati-b7ec7366d7d214d1ab33c6521405b74fd.dblock.zip.aes"
2025-12-08 12:59:43 -05 - [Information-Duplicati.Library.Main.BasicResults-BackendEvent]: Backend event: Put - Started: duplicati-b3f52cad89a0d44e69c25c72002584467.dblock.zip.aes (49.108 MiB)
2025-12-08 13:01:01 -05 - [Retry-Duplicati.Library.Main.Backend.Handler-RetryPut]: Operation Put with file duplicati-b3f52cad89a0d44e69c25c72002584467.dblock.zip.aes attempt 1 of 5 failed with message: Response status code does not indicate success: 502 (Bad Gateway).
2025-12-08 13:01:01 -05 - [Information-Duplicati.Library.Main.BasicResults-BackendEvent]: Backend event: Put - Retrying: duplicati-b3f52cad89a0d44e69c25c72002584467.dblock.zip.aes ()
2025-12-08 13:01:11 -05 - [Information-Duplicati.Library.Main.BasicResults-BackendEvent]: Backend event: Put - Rename: duplicati-b3f52cad89a0d44e69c25c72002584467.dblock.zip.aes (49.108 MiB)
2025-12-08 13:01:11 -05 - [Information-Duplicati.Library.Main.Backend.PutOperation-RenameRemoteTargetFile]: Renaming "duplicati-b3f52cad89a0d44e69c25c72002584467.dblock.zip.aes" to "duplicati-b25cd5b44a0fa44e5a6d60f033824b00b.dblock.zip.aes"
2025-12-08 13:03:44 -05 - [Information-Duplicati.Library.Main.BasicResults-BackendEvent]: Backend event: Put - Started: duplicati-bb67f648a3ec449b3978d8da44e60a346.dblock.zip.aes (49.204 MiB)
2025-12-08 13:05:02 -05 - [Retry-Duplicati.Library.Main.Backend.Handler-RetryPut]: Operation Put with file duplicati-bb67f648a3ec449b3978d8da44e60a346.dblock.zip.aes attempt 1 of 5 failed with message: Response status code does not indicate success: 502 (Bad Gateway).
2025-12-08 13:05:02 -05 - [Information-Duplicati.Library.Main.BasicResults-BackendEvent]: Backend event: Put - Retrying: duplicati-bb67f648a3ec449b3978d8da44e60a346.dblock.zip.aes ()
2025-12-08 13:05:12 -05 - [Information-Duplicati.Library.Main.BasicResults-BackendEvent]: Backend event: Put - Rename: duplicati-bb67f648a3ec449b3978d8da44e60a346.dblock.zip.aes (49.204 MiB)
2025-12-08 13:05:12 -05 - [Information-Duplicati.Library.Main.Backend.PutOperation-RenameRemoteTargetFile]: Renaming "duplicati-bb67f648a3ec449b3978d8da44e60a346.dblock.zip.aes" to "duplicati-b9a0e4d47e9b94d369be375b7a3491b94.dblock.zip.aes"
2025-12-08 13:12:54 -05 - [Information-Duplicati.Library.Main.Operation.FilelistProcessor-RemoteUnwantedMissingFile]: Removing file listed as Deleting: duplicati-b2b345574247d4b6997a41ee5c123becd.dblock.zip.aes
2025-12-08 13:12:55 -05 - [Information-Duplicati.Library.Main.Operation.FilelistProcessor-RemoteUnwantedMissingFile]: Removing file listed as Deleting: duplicati-b3f52cad89a0d44e69c25c72002584467.dblock.zip.aes
2025-12-08 13:12:55 -05 - [Information-Duplicati.Library.Main.Operation.FilelistProcessor-RemoteUnwantedMissingFile]: Removing file listed as Deleting: duplicati-bb67f648a3ec449b3978d8da44e60a346.dblock.zip.aes
2025-12-08 13:12:57 -05 - [Warning-Duplicati.Library.Main.Operation.FilelistProcessor-ExtraUnknownFile]: Extra unknown file: duplicati-b2b345574247d4b6997a41ee5c123becd.dblock.zip.aes.part
2025-12-08 13:12:57 -05 - [Warning-Duplicati.Library.Main.Operation.FilelistProcessor-ExtraUnknownFile]: Extra unknown file: duplicati-b3f52cad89a0d44e69c25c72002584467.dblock.zip.aes.part
2025-12-08 13:12:57 -05 - [Warning-Duplicati.Library.Main.Operation.FilelistProcessor-ExtraUnknownFile]: Extra unknown file: duplicati-bb67f648a3ec449b3978d8da44e60a346.dblock.zip.aes.part

You can Google search for below, or leave off part file to get more results

nextcloud 502 bad gateway part file

Duplicati or its WebDAV do change, but you don’t know when all was well.
Rather than try at random or get technical, asking provider may be simple.

12

with no changes other than log-file, backups have succeeded the last two nights as normal. i guess we chalk this up to infrastructure beyond my control; though i still think renaming an incomplete transfer invites trouble.

13

It apparently also invites trouble if you don’t rename, causing 2013 change:

Added auto-rename logic to work around faulty Apache WebDAV backends

I don’t know more details. Maybe the developer will comment, or maybe it’s
unreasonably hazardous to unroll it. I guess you want to retry original name.

That seems like it has the potential of running into the previous use of name,
whose status at destination might not be known, e.g. if you lost a connection.

Regardless, not my call, but there are at least two reports of .part file pain.
Possibly a workaround (except for space cleanup) would be to filter them out.