i have had the side winder with a 4600 and pushing it to 65mph on 3s i had no problems with it. also had a 9000kv cc motor on a mamba max on 2s hitting 80mph and still no problems with motor or controller. so perhaps the problem is a bad batch of shafts. the mamba max pro is a different story, i have one hooked up to a 13.5 losi motor and every time i turn the wheel for a split second it will throw it in to neutral or break. i have tried using sensord and smart sence mode and still the same thing. i even tried switching motors using a 10.5 and still the same. i suspect something with the jr 9100s servo but i have not had the problem when i had it in a car with the mamba max and a 5700.