That ESC is more than capable for a 21.5 turn motor sounds to me like the bec circuit gave out for some reason I had one that smoked on the same esc after some soldering on the motor wires as well I have 4 of these esc's and always keep a spare as well considering the price of them it is not that hard lol. if you bought it from hobbyking it does have a 1 year warranty on it just need to do a short video with the esc on and maybe a volt meter showing the output and than follow the warranty / return instructions on hobbyking you don't have to send in the defective esc they watch the video and than issue a credit took about 2-3 weeks for mine but still that is faster and easier thjan sending one back to the manufacturer.