I purchased this outfit shortly after it was introduced by AG. The sandals NEVER stay on the feet. Do these sandals now come with elastic backs (the little part that slips around the heel) rather than the useless non-elastic piece of material mine have? The little pieces I have don't stay on the heel, they just fall down and are completely useless, and so the shoes are pretty much useless, too. I'd like to call AG CS and perhaps trade these in for a new pair if they're now using elastic. Anybody know?