I agree,
It sure sounds like a HS problem and more specfically your resized cases. I have a couple thoughts..
1) Go I would back to basics,
I would double check the fit of the barrel to the receiver. (Yes I know its been back to the factory.... I learned long ago, NEW dosen't mean correct all the time) Refer to the FAQ's on the proper proceadure.
2) Then to the reloading proceadure, disassemble and clean the re-sizer die, re-assemble and set it up for your press. Using a smoked case that was fired from the chamber is question. (This can be found in most loading manuels. I like the Lyman) As suggested, you want to be sure you are not moving the cases shoulder.
3) Lastly, what about those primers? Are or could they be contaminated in some way? Personally, i will never actually touch a primer. Some may consider this overkill and say finger oils cannot contaminate. I simply prefer to remove all doubt and use tweezers if I need to actually pick one up.
Hope you can figure this out, I know how frustrating it can be.
Good luck,
CW