walks with a gimp

I'd say that your string and cables stretched before the loop slid down. Most of the pressure on the loop is on the bottom knot and your grip pressure pointis more than 1 1/2 inches below the loop. You should try a knot of serving about 1/8 of an inch below your arrow's nock and tie your bottomloop below that knot to prevent loop knot pinch on the arrow's nock.