HI Kassandra, As I understand it if humidity is too high during incubation the chick is too wet and can drown during/after pipping.
However, if it is too low during incubation there is not enough fluid around the chick to allow it to easily rotate just prior to hatching, and the inner membrane...
I think shrink wrapping is an incubator phenomena, -not sure if it is seen with broodies.
Low humidity during Incubation, (as well as opening the bator during lockdown) contributes to it, and makes the chick sticky so that it has a hard time rotating and hatching.
A lot of the "chicken" and "protein" in pet food is finely ground up feathers and some chicken offal and bones.
In some cheaper varieties of canned dog food you can actually see the coarsely ground up feathers.