It seems that the tracker DB was not correctly copied because of permission troubles... Too bad, but that's live. I found a not so old Backup on the device I made before upgrading from PR1.2 to PR1.3 so I could restore that.
Now everything works. Thanks again for the help.

I'll try to find a solution to create automatic backups. If I find something, I'll write it here in the forum.
BTW: Does anyone know how to make backups with the built-in Backup/Restore app through the command line?