I have a TQi tx and rx on my Tmaxx. The other day I was breaking in a new motor. I noticed I was loosing control of the steering and I looked at my iphone to see how the battery was doing. As soon as I noticed that the rx battery was going dead I headed towards the truck to shut it off. Then it takes off full throttle and I have no control. Why did the on-board fail safe not kick in?