If it turned without power, it was nothing inside the gearbox and the problem will likely return at some point.
It may be a wire problem, which you may have fixed while taking it off and putting it back on, or the wire shifted enough to make contact. Go back and check any splices you made. An inconsistent connection is hard on stepper drivers.
It may be a wire problem, which you may have fixed while taking it off and putting it back on, or the wire shifted enough to make contact. Go back and check any splices you made. An inconsistent connection is hard on stepper drivers.