FAV,check first for any loose screws.I put blue Loctite on the bracket screws,on the shaft.Gripper screws should not be a problem.I also put a thin pice of leather as a gasket,between bracket and riser.I have had more problems with the upper bracket than anything.This seems to happen when an arrow in the quiver is close to the upper bracket or it's screw head.Often,I got noise even if the arrow didn't touch.I have used a flathead screw instead of the dome head that comes on it and that can gain some space.
Just remove that particular arrow that is closest to the upper bracket screw head and see if that is the issue.I have also but a bracket off the hood and removed the upper bracket from the shaft.This really solved the problem.
Check for broadheads contacting each other or the hood.Even a broadhead point,touching the plastic hood,can sometimes cause noise.