Had this fault on both my mirrors, They can be repaired.
1 Remove internal door car and speaker grill.
2 Unplug the two cables from the mirror sockets
3 Remove mirror 3 x torx bolts and 1 x philips screw.
4 Pop out round disc cover from mirror housing.
5 free cables from sealent and remove mirror from housing.
5 Mark the end cap of the mirror motor assy to main body.
6 remove 4 x torx screws from end cover
7 remove motor assy from housing
8 remove motor from end cap and you will find that one locating pin is sheared off, this is what casuses the banginf noise.
9 Now for the fix, remove sheared pin from locating hole.
10 Drill this hole out to 3mm.
11 Place motor assy back onto end cover, location via the other locating pin, while holding in the correct position drill from the end plate side a 3mm hole into the motor steel cover. ie where the locating pin use to be.
12 Using a suitable self tapper screw secure the motor into position, screw from the end cap into the steel motor housing.
13 the screw must be vertually flush withthe motor cover to ensure correct assembly.
14 rebuild mirror and refit.
I have repaired both my door mirrors with this method and they are still working OK, after one year.
Thanks so much for this. Got my car yesterday and while fiddling about to learn what all the buttons did I managed to fold the mirrors in, but the passenger side one made that noise but did not move back. Definitely worth a try!