Ok, what I've done now:
- Factory reset
- Set up the ereader (log in)
- Connect to PC with calibre and stuff closed
- Rename BookReader and KoboReader files on ereader and copy the two files from the backup
- Pressed Eject in the toolbar in windows
- Screen kept showing "connected and charging" after eject, but Windows was no longer showing it as connected, so I pulled out the cable
- It briefly showed a list of books with reader percentage and the name as cover art cause the files didn't exist, but after a second they started disappearing one by one
- Turned it off and back on again, no books in list
- Connect it to PC again
- Open Calibre, this now shows no books as being present
- Send all by books to the device
- Eject it and the ereader imported everything. Everything shows up as unread
- Reconnect to PC and calibre
- Selected all the books with green checkmark
- Run update metadata with same checkboxes as in screenshot #2 (shows 14 books updated)
- Go to store/restore current bookmark and run restore with settings in #3
- Eject device
- Everything still shows as unread
I think the restore bookmarks didn't do a lot as I just created the columns earlier today and they weren't filled. That's at least what I was hoping to use the backed up sqlite files for.
I feel like the ereader simply isn't accepting the changed database, and as soon as it sees is it tries to "update" it which boils down to resetting it.