Likes to freeze on level 19 a whole lot! You have to get a lucky run where completing level 19 doesn't freeze the game.
Secondly, any level with blobs will occasionally glitch and the blobs won't be in the right places so you literally must die if this happens (ruining an otherwise perfect playthrough).
Thirdly, some of the high jumps don't always work correctly so instead of jumping onto the platform you instead might be bumped backwards and probably lose.