If I rescan a playlist (e.g. Add/Rescan a playlist already in the library), the operation fails to properly rescan the referenced tracks - for tracks already in the library, it fails to update in the DB any tags that have been changed in the track files.

Workarounds:
1) First delete the playlist from the library. You'll have to restore any references e.g. on the auto-sync list.
2) Rescan the individual tracks.

EDIT(TC) Tracked at http://www.ventismedia.com/mantis/view.php?id=6879