Parallax objects, when duped in the same pos/have the same id, can break a level.
Not corrupt it, but it'll keep the level from being saveable and will stop the level display from working.
Personally, the level would get stuck in "Loading level data" while the song played.
#Parallax Object bug
short wigeon
candid moat
untold herald
Is there any known fix to this problem? I have experienced the same issue and now my level is inaccessible.