Tip: Switch palace switches normally disappear if you replay the level. However, if you insert them as direct Map16 and use the hex-edit at $00EEB2 in the ROM map, you can replay the level without a problem.
Blame erik for not noticing
Thought for sure that thing was included in the original GPS. Dunno if I should update this or include it in GPS' next update though.
Anyway, sorry about that I'll fix it one way or the other.