[What's_nitro?]

Interesting problem, lutach. I will assume it ran perfectly in whatever vehicle it powered before.* Your motor wires look ok but I would check the little sensor wires and make sure there are no shorts etc. Maybe one plug backed out of the white connector? If a sensored system has issues with cogging, 99% percent of the time its a problem with the sensors. Also, have you reversed the servo direction? If so, did you re-program the radio afterwards?

*Wait, it's new. It didn't power anything before...