When doing a rescan of the collection with an already existing database, both the PlaylistBrowser and the CollectionBrowser show random double entries. After a restart both browsers show a correct display again. Still quite disturbing and could be misunderstood by the user to be a database corruption.
Created attachment 36153 [details] Screenshot with double entries in the collection browser
Yeah, I know. This isn't database corruption, but I don't know what it is -- I'm not really experienced with Model/View and TBH can't really follow the Collection Browser code, at least when I've looked at it so far. So not sure what the issue is. Someone more experienced with Model/View should probably be browbeaten into looking at it.
The double entries in the "Saved Playlists" are normal if they were imported into the database before, now they are imported to the PlaylistFileProvider (i.e. loaded directly). The way to solve this for you is deleting all of them and doing a rescan.
Unfortunately this doubling also happens a lot with normal tracks/albums. In some cases I believe some also disappear when they shouldn't, and Amarok has to be restarted for them to come back.
*** This bug has been marked as a duplicate of bug 172542 ***