I think I have figured out the problem and how to fix most of it. I do believe it is a vitamin issue, but I'm not certain if it is related genetically to the parents or just the chick itself. I have hatched a lot of chicks this year and have had 4-5 that were either looking up and flipping over, or sitting way back on its butt with its legs way out in front of it and would look so far up that its little head almost rested on its back.
I believe this is a result of lack of strength in its muscles to where it cannot get up on its feet and its neck muscles cannot support its head. I already add vitamin and electrolytes to the newly hatched chick's water, but I make sure to dip the weak chick's beak in it several times every 30 minutes or so, so that it has to drink some...careful of course not to drown it. After the second time of doing this, I hold the chick up to where it has to put strength on its legs. When I set it down and it falls back on its butt and starts to look up, I gentle push its head down to the correct position and try to get it back up on its feet. I was shocked at how fast most of the chicks snap out of it once they've gotten some vitamins in them and circulation to their muscles. I think when you push their head back down, they use a little of their neck muscles to push back against your hand and I actually had one stand up on its own just by being able to push against me. The worst one I had made progress as I worked with it, but took a full day to totally snap out of it. One person I had sold eggs to had a chick that did that, and after telling them what to do, they reported the chick was fine after 3 secessions.
I realize that if you are hatching many chicks on a regular basis, you probably don't have time to give a few individual chicks the extra attention or set them in a secluded area so that they don't get trampled. I'm just sharing this information so that anyone who may want to make the effort can...(if I'm correct in my theory)...understand a little more of what might be going on and give it a try.
I'm not completely certain about it being a genetic issue, but I CAN say that the last two chicks that I had do that were NOT from the same pen nor were they closely related.