halo, dudes
I have met a headache scenario on the left side mirror my X5 4.6is (RHD), it can be folded but cannot be retracted back to normal position. Really make me flat up

Initially, my car garbage and me thought it is just to change the Gear Set of the side mirror to fix the problem, but finally it is failed. My car garbage has tried to connect the side mirror with individual electric power other than the car, the side mirror could be folded and retracted smoothly in this way. However, it still couldn't be retracted with the power of the car. My car garbage said that the problem will be persist even changing the whole set of side mirror assembly, and don't know what a true reason it is, they just guess " the electric circuit (computer) for the mirror motor inside the left door to control the Left side mirror has been gone wrong ".

It seems like there isn't any assembly parts available to replace the electric circuit (computer) inside the door available in the market. Dudes, did you meet this problem before, and know how to repair it, or any assembly parts you can suggest me to buy in order to fix this problem

Thank you very much for your feedback in advance !!!