You find dried crust around the pip hole and on their beaks, or sometimes the pip area is still pretty wet if the pip is still on the down side when you find it. I had this problem when I had the humidity too high during the set and not enough fluid evaporated from the eggs leaving a lot left around the chick at hatch. Malpositions can be caused by setting the egg upside down and inadequate turning. Older embryos rarely stick to the membranes, that is why you don't really have to turn your eggs after 14 days of incubation. I still go by the book and turn until 18 days.
Some people think that it exercises the embryo.
Because I'd like to play around in my incubator I instituted a policy that I would never help a chick out of the shell. Whenever I'd help a chick out it usually was not doing it a favor. It was either weak, crippled, or would have hatched if I'd just left it alone. The chicks that dry out in the shell are usually permanently deformed because their bones have started to harden while they were still in the egg. Most of them grow up to be a little bent, but they are usually noticably abnormal in body shape.