Nocturnals are a much thicker nock, you are most likely getting pinch. If you don't have nock sets tied in you can just twist your loop a little for the fitment.Have you tried with standard nocks instead of the lighted nock? I am having a POI issue with Nockturnals. Trying to figure out if its a string pinch issue or what. No problem shooting broadheads out to 60 plus with standard GT nocks.