Hi, it's probably the type of clay. Sculpey (or any type of oven bake clay) shouldn't crack. If it's air dry clay it probably will crack since it shrinks when it dries, and since there is a wooden stick inside (which doesn't shrink) the clay will crack. Hope this helps!
+mikedude6951 Thank you! I had found a HUGE thick piece of foam and cut out some shapes out of it, and I picked up some clay from the beach for other shapes. I still wouldn't recommend either.