I'm having something like that happen too. Its only at night time when I use 2 joey bunz I think, unless its just that it is on long enough for shifting to happen. Its like the joey bunz slide below the snaps and then the top part sort of caves inward. It is driving me nuts. I should take a pic and see if its the same thing that is happening to you. She also doesn't have much of a butt so we have seen major crack by morning too. Thank goodness she didn't poo!