I am using 8611 per elevator half and each time I power the system ON, they chatter like hell. I know digitals chatter all the time, but this is ridiculous. If I place my hand under the elevator surfaces, kind of suporting them on its center, the chattering stops. Do the elevators need balancing???? are they are heavier on one side of its pivot point?? There is no binding at all anywhere during the entire travel. Just chatters in its resting position.