Tested with Build 1220. It seems like everything is working.

An other confusing fact was, that songs which were frozen with older BiaB-Versions, had no frozen-icon at the master-entry at the bottom of the mixer. Unused tracks, like the utility-tracks, appeared unfrozen after loading the song and all tracks were showed. The status of the the song was "All tracks frozen". After a new "Freeze All Tracks" the unused tracks were displayed as frozen too. In combination with the bug, that the tracks didn't disappear, the confusion was perfect!

It seems, that unused tracks are marked as frozen, is a changed behaviour in younger BiaB-Versions.

Thanks for your posts!