Meaning you backup again, and all is OK? Have you looked (e.g. in the Search box) to see if file is there?
The file delete is retried 5 times by default. In the example below, a retry delete finally got rid of the old file.
You would need to set up logs to be sure, but the one here had a series of upload failures, each of which leaves things in an unknown state. An upload retry is done under a new name, and old potential messes resulting from failed upload get cleaned up at the end. You can see some confusion where Google won’t delete the file because it thinks it’s not there, but then a file list by Duplicati sees it, and warns you of that.
Retry of delete then failed because Google said file wasn’t there, but files list this time saw it was gone.
In the example below, everything ended well (it appears), but you can see if your file was actually deleted.
Generally it would be, as I think retries persist up to the configured limit. Failure is an error, not a warning.
Duplicati can’t control Google, but if this gets too noisy I suppose Warning could be turned to Information, which won’t do any popups but could be gotten if someone really needed the detail to look into a problem.
Warning at end of job after Upload Retry turned down the noise level a bit. Maybe it needs to lower more?
Excerpt:
2020-05-13 19:00:55 +01 - [Retry-Duplicati.Library.Main.Operation.Backup.BackendUploader-RetryPut]: Operation Put with file duplicati-20200513T180000Z.dlist.zip.aes attempt 1 of 5 failed with message: The remote server returned an error: (403) Forbidden.
2020-05-13 19:01:05 +01 - [Information-Duplicati.Library.Main.Operation.Backup.BackendUploader-RenameRemoteTargetFile]: Renaming "duplicati-20200513T180000Z.dlist.zip.aes" to "duplicati-20200513T180001Z.dlist.zip.aes"
2020-05-13 19:01:07 +01 - [Retry-Duplicati.Library.Main.Operation.Backup.BackendUploader-RetryPut]: Operation Put with file duplicati-20200513T180001Z.dlist.zip.aes attempt 2 of 5 failed with message: The remote server returned an error: (403) Forbidden.
2020-05-13 19:01:34 +01 - [Information-Duplicati.Library.Main.BasicResults-BackendEvent]: Backend event: Delete - Started: duplicati-20200513T180001Z.dlist.zip.aes ()
2020-05-13 19:01:34 +01 - [Information-Duplicati.Library.Main.BackendManager-DeleteRemoteFileFailed]: Delete operation failed for duplicati-20200513T180001Z.dlist.zip.aes with FileNotFound, listing contents
2020-05-13 19:01:36 +01 - [Warning-Duplicati.Library.Main.BackendManager-DeleteRemoteFileFailed]: Listing confirms file duplicati-20200513T180001Z.dlist.zip.aes was not deleted
2020-05-13 19:01:36 +01 - [Information-Duplicati.Library.Main.BasicResults-BackendEvent]: Backend event: Delete - Retrying: duplicati-20200513T180001Z.dlist.zip.aes ()
2020-05-13 19:01:46 +01 - [Information-Duplicati.Library.Main.BasicResults-BackendEvent]: Backend event: Delete - Started: duplicati-20200513T180001Z.dlist.zip.aes ()
2020-05-13 19:01:47 +01 - [Information-Duplicati.Library.Main.BackendManager-DeleteRemoteFileFailed]: Delete operation failed for duplicati-20200513T180001Z.dlist.zip.aes with FileNotFound, listing contents
2020-05-13 19:01:49 +01 - [Information-Duplicati.Library.Main.BackendManager-DeleteRemoteFileSuccess]: Listing indicates file duplicati-20200513T180001Z.dlist.zip.aes was deleted correctly