I got that bug too, but it occurred only the first couple of times I started the game. After that it seemed to have fixed itself...

Anyway, I got 2 more suggestions for the next update.

1: Make ambient lightning work outside of water when water is used. Either that or make it possible to remove the water from the level completely (until you activate it again) so you can have lightning again.

2: This has undoubtedly been asked a couple of times before, but, maybe add some event to change the music in the level? You could do it either with text strings like you did with the level exits, or use the Bonus/Secret Level field in the Level Properties window, or something else you think is better.
As for possible parameters, I'm thinking of both fade out and fade in (measured in gameticks or seconds), pause between the eventual fades, and if you use text strings, you'd need text and offset of course.