In the main game, the headless tanks in Zcor - 2 have no hitbox. On Korb - 2, when the spinning things knock a ball out of the way, it will occasionally only move the image of the ball, but not the ball itself if that makes sense. When you constantly collect balls for a few seconds, the music will cut out. Most apparent when collecting a previously placed string that you couldn't connect. Also, at the end of each song it usually pauses a bit before restarting.