What Causes This?

Plug in the battery to do a calibration and the Right Rear motor starts to spin approx 1/4 rev then stops, (like it got a current spike) while the flight board is booting . . . after it boots the same motor comes on at maybe half throttle and stays on.

Swapped Right Rear and Left Front motors and problem went away.

I can’t imagine how that could have solved problem you mentioned. Perhaps rebooting? Cold solder joint which you temporarily “fixed” by stressing the board in the process of swapping the cables? A drop of dirty water on the PCB which dried out while you were swapping cables? Who knows, but not swapping motors. No way. :slight_smile:

Maybe I’ll swap back and see if prob reappears. Agree with you wholeheartedly, but I rebooted several times in original locations.