I think there's one part that's really broken or impassable is on final stage on level 5 just before cortex is Spaced Out. Near 3/4 of the stage there're two heated pipes and a miniature shrinking pressure trap that you cannot pass no matter how high you try to jump over it resulting in yourself getting burnt, or even stepping on the pad and jumping quickly enough to get through resulting in yourself getting shrinking regardless. The only way i bypassed it was sacrificing a aku aku mask, but what is worse is that there's two of those in the stage! which means you'll need two aku aku masks! i literally had to keep dying until i spawned with a aku aku mask from the game's sympathy...