Robert,

It sounds like your brakes aren't adjusted right maybe? Either that or your radio might have some weird settings in it. I'm not sure about the Magnum as I have a GST and Skyion DSX but when I'm going full throttle and I slam on the brakes, this damn thing stops on a freakin dime. If I adjust them any stronger it would flip itself over for sure.

Also I don't know about your manual but in mine that came with the GST it instructs you to turn on both radio and receiver and walk away from your car to check range, which might have helped diagnose your radio issues before it was fired up and running. You're lucky your car didn't take off on you..

Good luck!