Thanks for the advice crystalworks.

I suspected maybe a solenoid at first, but the trans shop did not fault anything but the wiring connector, during the service and testing.
I guess I should have asked them to investigate the sluggish reverse selection more thoroughly, having initially mentioned it to them when dropping off the car.
I just assumed all was good when they made no further mention of it, after servicing and test-driving the car.

Will look at doing the mirror switch/sensor cleaning, thanks.

__________________

Current:
2004 X5 4.8is - Le Mans blue/Cream beige
1994 E31 850CSi - Sterlingsilber

Previous:
1987 BMW E28 M5 - Delphin-metallic
1976 BMW E3 3.0Si - Arctic-metallic