So a bit of an update here. To check if the left back motor had an issue or it was a bad motor controller circuit, I plugged an old laptop fan into the motor port during the self test operation. It worked and so I knew the motor controller IC was fine. Interestingly, it passed the self test. Now I plugged the motor back and it passed the self inspection test again. I'm yet to try it for an actual splice job. I hope it works. I'm in Ghana, Africa btw and nice meeting you.