Bill, I have never ever had a problem with the old AA's but, I have had this happen to me with the new style AA hulls for my 12ga loads. Seems to happen on the final crimp. Your wad pressure seems about right for the info Winchester has made available on their site for loading the new style hulls. You may have to make a slight adjustment to your pre- crimp die, as this is another suggestion they make.
I seemed to find that by applying a pretty solid downward pull, slow but sure on the primer seating stage, and then doing the pre-crimp twice, after turning the shell, before final crimp eliminated this deformation. I suspect as others have mentioned that the basewad may move up slightly when inserting the primer, and the gas seal on the wad is catching the upper lip of the basewad, and deforming the side of the hull during final crimp.
I notice a slight resistance on the primer seating, and I think the slight more pressure may re-seat the basewad. I have not adjusted my shot wad pressure at all,(less than 20lb) which I suspect is Winchesters way of making sure the basewad is forced back down. I am still not sure what the pre-crimp stage would have to do with preventing the deformation, other than perhaps settling the shot down into the shot wad a bit better, so there is less pressure on the hull wall?
I am sure some with a more brilliant mind than mine might offer a better explanation, this is just my feeling, about what causes the problem. Doing it my way does hamper the speed of loading, but has eliminated the deformation.
I think we will all be loading STS hulls one day, when the last of the old AA's disappear.