That is pretty weird. I am too new to have experienced something like that yet. What temp are you incubating at? Have you had other clutches in the same incubator from different parents? Were those clutches healthy.

If it is genetic it is being carried by the male since clutches from a possibly related and non related female had the same spine twisting in the offspring. I guess the related offspring would probably carry the same genes even though they do not visual show the twist.