Welcome to the forum @mhas
In my testing, it seems to be looking at dblock files, so there’s a suggestion that the dindex are extras.
Partially Solved - Missing volumes; attempting to replace blocks from existing volumes has some ideas.
If you want to go deep technically, great. If you want to point to a DB bug report, someone else can help.
EDIT:
On the other hand, such errors may indicate a real problem. Showing the errors would have helped, but
sometimes they’re hard to find. Keeping a copy of the old database would also have helped. Few do so.
EDIT 2:
Sometimes errors are in About → Show log → Stored. About → Show log → Live → Warning helps too.
The per-job logs are in the job database which might be gone, but you can see if you have the older logs.
Looking in the database folder is also good. I think there’s at least one case which saves a backup copy.