[Ajtozzi]

Make sure that the primer seater is properly seated in the ram. Take the shell holder out, raise the ram about halfway up, slide the primer seater in the slot and make sure it goes ALL the way down, then slide on your shell holder. Also make sure there are no spent primers stuck inside that are causing the primer seater to not seat correctly in its mount.

I've had the same issue a few times. Taking it apart and putting it back seems to work every time.