How dry was your bator? I was keeping mine at 70-85% depending on if a chick was hatching (it would go up) so that should not have anything to do with a thick membrane (at least that is what I believe) Maybe some breeds just have tougher ones???
Then again, I only had to help the two out. The other quitters did not pip. It was not because the eggs had not lost enough of moisture though, because when I cracked them open to see, the air cell was big enough.
I just don't know, I think it has to do with those tough membranes. But why are some too tough and others are not? Was the chick weak or the membrane to strong? Anyone have answers?