What bow are you shooting? Is it a real short ATA? I'm kinda at a loss for suggestions, but maybe your string angle is so accute that you are damaging the nock from pinch with your release and making it get brittle over time. I'd definitly take a serious look at that. You don't want a nock coming apart at the shot. Possible dry fire and injury might happen then you'll have bigger problems. You definitly want to make sure those nocks are snug inside that arrow too. If they are loose, that will eventually cause problems as well.

A string loop will help pinch if that's the problem. Some short ATA bows you almost have to shoot with a loop to keep you arrow from falling off if you have to let down and to eliminate nock pinch.