If you're shooting something like the ICS Hunters or similar carbons with the standard carbon nocks just pushed in.. this is going to happen, especially if you shoot HARD surfaced targets. The problem is with the nock free floating in the shaft when it impacts the target the momentum of the nock continues and in a real sense slams into the back of the shaft at the shoulder. Over time the shaft actually begins to split or loose stability. You can try a new nock to see if it's better... but either way you'll end up with the problems described. The best solution to a carbon arrow is to glue in ACC nock adapters and use the ACC nocks. You'll have to sort out the size for your shaft. What this does is add a TREMENDOUS amount of shaft stability. You will no longer have shafts cracking and you'll never have the nock problems again. Take your existing nocks and push on them sideways in several directions around the shaft. See if there's give or you actually see cracks. Eventually they'll come without a glued in insert. It adds a few bucks to a dozen arrows to glue in the inserts... but the shafts last forever.