Usually only individual files become corrupted. If your Things JSONDB file became corrupted then it would only impact Things.
When ever something doesn’t work, the first place to look should always be the logs. Do you see errors in the logs?
If you are willing to run the risk you should have automatically created backups of your JSONDB files that you can try to restore and see if it’s just a problem with your one file or a wider issue. The logs would be informative.
The automatically created backups are in /var/lib/openhab2/jsondb/backups.
I recovered the jsondb folder from backup and since then it is working.
I could not see any errors in the log - any other indication for corrupted file system, which I could look for?
But I take your concern about corrupted file system seriously and will update my backup strategy. I noticed that my existing backup only backup openhab (amrecover) but not the entire system. Any advises on backup solutions for Raspberry in combination with Openhab?