If it's not the timing, it might be due to bounceback of the prongs from hitting the shelf on the bow. Even though the QAD is dampened to prevent bounceback, if the prongs hit the shelf hard enough, they'll bounce back and touch the vanes.
The remedy is to raise the nock point about 3/8 - 1/2" higher to give the prongs more clearance over the shelf. The arrow shaft will be above the arrow rest bolt hole. It'll still tune good like that. I have to do that with my PSE bow that has a QAD Ultra Rest.