Databases MUST match the contents of the device. I can't believe things on your device have not changed in a year
I would say your DB has become corrupted and must be rebuilt.
You must logout of the device, then log back in for it to rebuild.
You will lose a bunch of stuff like Reading Position, notes.
(If you stay synced with Kobo, this might not be as severe)
Not much choice. It will get worse. The Q is when it gets so bad you can't read.