Welcome to the forum @namsevz
This looks strange. Is there really an updates folder below the updates folder?
What’s in it? changelog.txt (if present) will reveal the release. Is it lots of files?
If I tested right, 2.0.5.1 folder Properties should list as 574 files and 82 folders.
Duplicati checks update integrity before running, so might have not run 2.0.5.1,
meaning you reverted to the 2.0.4.23 base version which can’t read newer DB.
EDIT:
Downgrading / reverting to a lower version says how to intentionally downgrade.
If somehow your 2.0.5.1 went bad and is hard to fix, downgrade it then upgrade.
Alternatively, install from .msi again as an Administrator, and get a good 2.0.5.1.