I am having problems with Engine DJ and playlists. I am unable to do anything with playlists. I can not edit, update, add or even add tracks to the playlists. This started happening a couple of days after I updated to 4.2.
Have you tried downgrading to 4.1.x with your database backups to see if that resolves the issue? Trying to isolate if 4.2 is specifically the problem.
When you say “Backup” is that the copy of the database that Engine provides or something you’re doing manually? And are you backing up the databases on your USB media as well? That matters too. IIRC Engine doesn’t backup the databases on external media.