I've been dealing with the same problem. Are you hearing a loud noise upon release of the arrow? Through video and audio I discovered that the back of my shaft was striking the shelf upon exit. This was the result of the nock high flight, and also prevented nock set adjustments from making any difference.
I'm not sure if this is the problem with which you are dealing, but I finally discovered that I could correct it by inserting a piece of leather under the rug on the rest (I've also heard of folks using a section of a toothpick in the same manner). This raised up the rest by about 1/8" and decreased the amount of surface area that the arrow contacts on the rest. I'm not sure of the physics of it, but it helped to alleviate the problem for me.