'05 Mathews Outback, 3 pin Impact collector sight, trophy taker drop away, 70# 29" using 28" goldtip XT hunter 100 grain 5575's. I think thats everthing. I have been pounding my target accurately for 3 months. This morning I shot and was way low. Thought that I had to tweak my sight a little and ended up lowering the sight almost to the end of the track...Still low?? Then I noticed that my kisser button and 2 nock collars around the string were sliding up the string after release. So I moved the sight back to where I had been accurate, and slide the nock collar points and kisser button lower, until I was accurate again. But they continued to slide up after release. Is this common- after a while do they need to be replaced when they start sliding?? What causes this?? Thanks for any and all input...