Sounds like a case of extra hard cups on the primers. I think that is what is happening with mine. I still have factory springs in my guns and have had no misfires on that account.
The Winchester WLP primers I have are much harder to seat than the CCI primers I have.
Companies can produce products at times that are a tiny bit out of spec and have it get out the door on them. I have had thin primers from other companies that blew out at the edge under standard loads before. This just went the other direction.