I have had this problem happen occasionally, after reverse, a passenger window reverse mirror would 'stutter' while retracting back from downwards position. 

 

Not sure if the mirror engine is failing, or its related to maybe some residue from pressure washing inside the mirrors?

 

https://www.youtube.com/watch?v=h5yIlOT8sR4&feature=youtu.be

 

You cant see much of the mirror moving back in the video, but you can definitely hear the fault sound which is always preset when this happens.

Edited 13 October, 20169 yr by toni8b

I don't know the answer to your problem, but just noting that's a ridiculously loud sound from a mirror motor.

The electric motor on my RS mirrors aren't that loud so I suspect it's stripped a few cogs on the plastic gears which is causing the stuttering and excessive noise.

But this 'stuttering' noise (not sure how else do I describe it) only appears when this fault occurs and the mirror wont retract to its normal position.

 

Had this happen several times during car's lifetime. After I set new position into memory (which I have to do, because it looses previous position), then it works. And when it works, sound is normal.