I have a new xerun 120a that I am having problems with. When installed in a car, and the car is on the ground, it will not move when I apply throttle unless I give it a little nudge. When the car is held in the air, it will usually move. Also, it makes a faint high pitch sound that I haven't heard my other 120a make. I have double checked the sensor cable, and also tried a different one, still no good. Any ideas? I got it at hobbypartz and am trying to get it RMA'd, unless you guys have any idea whats going on that I can fix.