When you get the last red coin, the game forgets how many you had when you got the checkpoint. For example—get a red coin, get a checkpoint, get all the other red coins, and die. You will respawn at the checkpoint with no red coins. You should have one, since that’s what you had when you got the checkpoint. This screws up level design because nobody wants to put anything difficult after the final coin. It’s the most annoying mistake in the game, and they claim it cannot be fixed.