That metallic throttle cable acts like an antenna as it passes through the RF field that exists around the igniton module, battery, switch and the motor. It will bring that RF right into the servo and hence the receiver. It doesn't happen all the time but just enough to result in a crash every now and then. It makes no difference if it is making metallic contact with the engine or not. It works just like the antenna receiver. Use a non metallic pushrod to be on the safe side.