Have you checked to see if the ring on the transfer bar is broken off ? That's what happens to mine when your problem happens.Have RCBS Grand, actually two of them. Recently on one of them the primer feeds to the transfer bar looks good going to the shell plate but maybe one out of 20 times it turns on it's side or flips completely over. I discover this when pulling the operating handle and feel resistance. So stop and look to find primer on it's side or flipped over. If I'm lucky the primer has not been crushed. Anyway any idea's what may cause the primer to flip once it gets there?