I also have found a bug. I dunno if someone else has seen it.
In the stages 5 and 6, sometime the background gets red instead of the normal background. I got it twice. Once in a run of Legacy Mode (where I only made it to Stage 5 and using all the continues) and another one while the stage 5 boss was poundering me in Pointdevice Mode (the bug persisted in Stage 6. It fixed itself when I restarted the game).