Maybe a bad system. I had to return my new Sidewinder becouse it kept running very hot and cogging during full throttle. Smooth off the start thou Even the Castle guy was confused. New one rips! No issues at all! But maybe try trouble shooting if you can. Try a different servo. If you have a HT servo it might be straining the ESC. I cant run my Power HD 215oz servo with my Sidewinder system. But other servos Ive tried that are less torque are fine. Ive read that Castles internal BECs are weak. But maybe try other batteries, radio maybe. Im not shure with the still running but not over 10 mph. Im still learning myself after a year. change gearing. Adjust ESCs settings maybe. Turn up/down punch, timming, etc. I would try everything befor returning my new stuff and waiting 2 or 3 weeks before gettin it back.