Cheddite primer decapping problems w/AA hulls

[Warhammer4k]

For at least 5 years, I've used nothing but Winchester AA hulls and Cheddite 209 primers when reloading 12 ga. shells.

In the last year, I've started having some of the spent Cheddite primers fall apart during reloading. The primer punch only removes the silver primer cup, while the copper-colored primer body stays in the hull. I end up having to throw away around 10% of my gray AA hulls, because they have the primer body stuck in them. There is just no way to get them out.

What is going on here? Did Winchester change something about the AA hulls? It seems I only have this problem with the gray AA's.

I have been loading from the same lot of Cheddites all along. It is only as I get down to the last ~2000 Cheddites of a case of 5000 that I have started having this problem.