[Jon Stratis]

Try swapping the leads with another wheel - basically, power the front wheel with the controller for the back one and vice versa. Hopefully, one of three things will happen. It works fine, telling you there was a loose wire somewhere, The original wheel stops spining again, telling you the issue is with the motor or some sort of mechanical issue, or the back wheel stops spinning, telling you the issue is with the speed controller, PWM, or PDP. It will at least help narrow down the possibilities!

Also, have you verified you aren't popping the breaker for that wheel?. A loose connection could cause increases current on that wheel only.