That one really sucks!
I tried to fix it myself by forcing the engine to play the correct music using additional screenplay. However, this causes levels with a specified song in the settings (and without screenplay) not to automatically play the levels’ song, but to be all quied. The music also won’t start playing after a longer time of waiting. So this time it definitely cannot be an issue of a too slow loaded music file.
What a shame! Since I need to make sure the correct music is playing and I just cannot do it for now, I better wait for a fix. I don’t want to insert tons of unnecessary screenplay, which possibly not even work. Hopefully, deWiTTERS can get rid of this soon.