If you use a known good backup of the same file? Test
If you use another troublefree database or create a new one from template and test?
Narrowing it down to application or document is a good first step.
Dupe the database in the OS level and open on another computer?
Save the database as Smaller and test.
There are articles about corruption and steps to test and repair - although using a known good backup is always recommended.
So we recovered the file, migrated it to FM 12 ( to mitigate any possible application problems) and the problems seem to have followed. It's doing the same thing.
Recovering and migrating the file does not guarantee that you have eliminated damage to your file. Since this did not happen in the past, I'd import the data into an older back up file and test to see if that corrects the problem.