dsnyder

I don't have any information on the GWS equipment, you would need to contact them for that. If the 811 does that however, it can be a number of things. It could be a bad extension, slop in the linkages or control horns, servo arm fit on the servo, servo mounted too rigidly (servo screws too tight, servo eyelets installed in the incorrect direction, servo mounting rails too tight against the servo), a dirty connection between the servo and the receiver, too high of voltage, a bad battery, switch, loose hinges, hinges that are too stiff and don't allow easy movement, any binding, etc. The 811 also is a single ball bearing servo, which means there is a small amount of play possible in the output gear, and with the centering power of the 811 it can cause some small jittering. If you can lightly touch the control surface when this is happening and it stops, it will not happen in the air due to the air loads on the surface, so it is fine to fly. If it doesn't stop, the pot may be worn in the servo.