Can eggs crack when positioning themselves for hatching?

[Diveks]

I’ve already posted about the same clutch (different issue) last thread. I’ve never experienced anything like this with all different types of eggs I've hatched.

I have been hatching some lovebird eggs and this clutch seem to have an issue. Im not sure if the parents are calcium deficient since they have only been with me for 1-2 weeks before laying. Got two pairs from a friend of mine. One pair kept cracking the eggs and female of the other unfortunately passed (maybe a calcium deficiency?)

Well one chick is currently 3 days old now (was a stuck chick that i had to assist). The second chick was severely malpositioned and passed. Well now egg 3 and 4 is pipping. But they pipped almost 48 hours ago, I did not help as when i candled them they looked to still be 1-2 days from hatching. Their head and beak was still facing down and getting into position. The crack seem to have started from the back of their necks and not in the air cell.

Illustration to show how they looked (from: https://www.backyardchickens.com/threads/goose-incubation-hatching-guide-completed.491013/)
Day of pip:

Today: (more shadowing)

They are still alive and moving around. The pip is getting bigger and more noticable. So which one is the real pip 2 days ago, today, not yet? Heres a pic of the eggs they both seem to have more than one ‘pips’. no beak in the candling just yet. I keep the room at around 60% but still try to take them out as little as i can.

Forgot to mention that i haven’t made the latest aircell line it is far down now.

 

[Stipenvlerk]

Not an expert since it never happened to me in an incubator but I would say it's possible depending on the surface (is mom is on a pile of rocks or something...) but not very likely in an incubator.
Could they have been turned after they start pipping?

 

[Diveks]

Not an expert since it never happened to me in an incubator but I would say it's possible depending on the surface (is mom is on a pile of rocks or something...) but not very likely in an incubator.
Could they have been turned after they start pipping?

Hmm bizzare, so the fourth egg just hatched out an hour ago. They are now in an incubator but mom was taking care of them before she passed. As far as i know only one has a crack from one of the two moms (one passed one cracked the eggs).

Edit forgot to add: I stopped turning once i saw they are drawing down. But usually at the same time they are already pipped, but never in the air cell always somewhere low… should be where the back of their head or back is.

The third egg is peeping loudly but ill let it try to go out on its own first. Also the fifth egg “pipped” this morning. Hm maybe they could pip and turn? And then turn again and pip from another hole? Could the back of their necks be so strong that they crack the egg? I guess as long as they are healthy I am okay. Just worried that the shells are so thin that it affects the hatch rate.