Have you tried to crank the poundage all the way up so that the limbs are touching the bottom of the pockets and then shoot the bow for a while?

Are the draw lenght modules tight? Maybe it's slapping the inside of the cam every now and then.

Is he using a metal D-loop? If so is it slapping anything else on the bow at the shot?

Are the fletchings maybe hitting the cables every now and then at the shot? I had this problem with my bow when I installed a NAP QT2000 drop away.