# How to fix this fatal backup/repair error

**URL:** <https://forum.duplicati.com/t/how-to-fix-this-fatal-backup-repair-error/21780>\
**Category:** Uncategorized\
**Created:** [January 9, 2026, 1:54am UTC](https://forum.duplicati.com/t/how-to-fix-this-fatal-backup-repair-error/21780 "2026-01-09T01:54:09Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![StevenKSanford](https://forum.duplicati.com/user_avatar/forum.duplicati.com/stevenksanford/32/2236_2.png) [@StevenKSanford](https://forum.duplicati.com/u/StevenKSanford)\
**Post date:** [January 9, 2026, 1:54am UTC](https://forum.duplicati.com/t/how-to-fix-this-fatal-backup-repair-error/21780/1 "2026-01-09T01:54:10Z")

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I’ve gotten the same error from a backup (previous backup was killed after stalling for two weeks) and subsequent repair attempt:

2026-01-07 21:55:52 -05 - [Error-Duplicati.Library.Main.Controller-FailedOperation]: The operation Backup has failed ConstraintException: Detected 16 file(s) in FilesetEntry without corresponding FileLookup entry

2026-01-08 20:30:51 -05 - [Error-Duplicati.Library.Main.Controller-FailedOperation]: The operation Repair has failed ConstraintException: Detected 16 file(s) in FilesetEntry without corresponding FileLookup entry

How do I fix this?

Thanks… Steve

MacOSX Tahoe 26.1

Duplicati 2.2.0.102

Macbook Pro w/M2 chip

Destination: Google Drive

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**Author:** ![Marc\_Neiger](https://forum.duplicati.com/user_avatar/forum.duplicati.com/marc_neiger/32/567_2.png) [@Marc\_Neiger](https://forum.duplicati.com/u/Marc_Neiger)\
**Post date:** [February 1, 2026, 9:07am UTC](https://forum.duplicati.com/t/how-to-fix-this-fatal-backup-repair-error/21780/2 "2026-02-01T09:07:23Z")

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Duplicate of #21699 ?

> [@Detected 7 file(s) in FilesetEntry without corresponding FileLookup entry](https://forum.duplicati.com/t/detected-7-file-s-in-filesetentry-without-corresponding-filelookup-entry/21699):
>
> I just got hit by this on one system. I know it’s over loaded system, and there might be reasons why it’s likely to get “any issues” if the logic is broken on some level. Ie. race conditions etc. I updated to latest version. Tried repair, didn’t work out. Saved the full old backup set and then did full reset. I did save backup files and database, if some extra information is necessary. I also updated to latest beta hoping that the source of this issue has been fixed in it. Just hoping that the …

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<div class="post-metadata">

**Author:** ![StevenKSanford](https://forum.duplicati.com/user_avatar/forum.duplicati.com/stevenksanford/32/2236_2.png) [@StevenKSanford](https://forum.duplicati.com/u/StevenKSanford)\
**Post date:** [February 2, 2026, 9:30pm UTC](https://forum.duplicati.com/t/how-to-fix-this-fatal-backup-repair-error/21780/3 "2026-02-02T21:30:43Z")

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I tried deleting/rebuilding the database several times, rerunning (same error), then started deleting database versions. This created a different error about missing blocks (sorry, I lost the log when I deleted the database). No one had been able to overcome the new error, from what I could find on the forum.

Anyway, I finally gave up, deleted the database, renamed the online file folder (Google Drive) to keep as an archive, and started a new backup from scratch. It took several runs over several days to create the new backup (Google only allows so many file uploads per day, so I got a log of “403” errors), but now I’ve got a current backup.

It seems like an Achilles Heel for Duplicati that it cannot recover successfully from an interruption while backing up. Any thoughts?