JJ2+ crashes or freezes on Single Player levels (from my experience, either in levels with scripts or in levels with custom music) when one of these actions happens:
- Press Esc, then New Game, then confirm;
- The music track in the level changes;
- Press the X button when the game is windowed.

It doesn't always happen and, from what I can tell, if it doesn't happen the first time after booting up the game, it never happens during that session. I didn't test it too much, I noticed these issues while playing Jingle Jumble and Valen Village.