I wonder if anyone knows what causes this?

Have eggs in bator, but they are dropping like flies. Temps are right on the nose. When I break the egg to look (which I always do) I find that the yolk is not attached to the belly of the chick, like it should be. THe chick looks perfect, except for very small, but the yolk is not attached getting ready to be pulled into the body. Instead it is a smashed mess floating around the egg.

They are turned by hand, no turner. I am gentle. THese eggs got very cold, perhaps even frozen before I set them. I cannot imagine they would come this far and fail now because they were frozen when I gathered them? You'd think they just wouldn't start if freezing was the problem.

This is very annoying.