Your capper seems to be a mirror image of the two I have, from different makers. On both of mine, the spring side of the jaw cuts the left side of the nipple recess, as viewed while capping. I guess it would be the clockwise edge. In any case, I have resorted to using a dowel with a shallow hole drilled into the center of the end to grip the cap. It is very slow, and the extra adrenaline when I'm loading on the line at CAS matches makes me very clumsy. I will probably end up filing or using a Dremel to relieve the damaged edges, or I guess I could just let the capper do the work and reblue once the cuts are deep enough so they no longer rub!