I'm having trouble with my KS-5 punching the primer deep enough to fire. It happens infrequently but it's a pain. Once. it was 5 out of 50; the next time it was 2 of 50. I brought it to a friend and he cleaned it and fired the shell I gave him, in his own gun, and it fired. He tried it with 5 shells and only four fired. The last one had a very small dimple in the primer. Has anyone any suggestions as to this problem?