I have the exact same bow and a very similar problem.... It was driving me nuts. It would shoot fine most of the time but every once in a while when I shot, it would make a "twang" noise followed by a horrible shot. It got worse as time went by and I started noticing wax on the fletchings. I realized the wax is bow string wax, so I checked the cable guide shaft (the shaft with the red guide sliding on it) Sure as heck, with the bow at rest, there was clearence for the fletchings, but the shaft was loose. I rotated the shaft to increase the clearence and tightened the lock nut. Problem solved and it still shoot like new. I believe mine is also seven years old too