You would be suprised at the little things that will mess with your sights. Any little thing can screw them up. Once when I was waxing my string I moved the silencers on the string and the cable and was off like 6" after that. I have had things come lose on me when shooting. So now when I start shooting bad I stop and take a look at all the scews and give everything a push to see if it is tight.