The __db.00x files are only internal files for Berkeley DB so not helpful
But yeah you can try the db_dump command (db-utils in apt) on your wallet, it should output a bunch of (sensitive!) hexadecimal data without errors
I just tested with an old wallet of mine, maybe from something like 2013, and it worked as expected
If it works for you then try deleting (backup them if you want but they aren't needed) the __db.00x files