There was no movement visible when I candled the egg, I usually go off that too. It was just a dark band around the middle off the egg, clear at both sides of it.
The chick wasn’t underdeveloped, it was developed enough to be a day 17 chick which is what’s confused me as to why it was squashed into such a small part of the egg
These eggs were from posted eggs so some of the eggs will have been from the same bird but not all of them. Their air cells weren’t detached either.
All the eggs have been in the same incubator, temperature is running correct. It’s my first time using an upright incubator though, I usually use flat ones.