Was this clutch of eggs from the same parents as last years clutch?
I have a theory that a lot of kinks and still births are the result of borderline vitamin deficiencies in the parents. This was after I lost a female Burmese python and her whole known fertile clutch of eggs because her food items had had the liver removed. Liver is the major vit A repository.
I suggest putting a drop of a good cage bird liquid multivitamin in the belly of a dead rodent before feeding it to the breeders, once a month. I suggest a cage bird vitamin because birds use Vit D3, as do snakes, and human vitamins have D2, which is not as good. Ball pythons should get plenty of calcium from rodent bones.
For what it's worth, I use Avitron, from Lambert-Kaye, simply because the local pet shop had it on their shelves. I have never given this stuff to ball pythons, because I don't keep ball pythons. But I have given it to half a dozen corn snakes without obvious ill effects. Good luck.