While I don't know "for sure" what stops the mirrors at either end of the travel I "think" it's just a physical stop.
I base that on my experience of "gunged" up mechanisms that I lubricated. And what I saw when taking one off with the intention of replacing it, though actually just lubricating it.
Based on all that, including operating the mirrors off the car with a simple 2-wire 12v supply I think moving the switch merely sends a voltage of the correct polarity for a fixed time (about 10 seconds) to the fold/unfold motor.
When it hits the physical stop it just stops the motor until the power cuts.
When my mirrors were "gunged up" they would only partly fold or unfold, but twiddling the knob quickly into reverse then back made it move a further sluggish step, supporting the "timer" hypothesis.
On that basis I'd say the end stops have been broken off and you'll need new mirrors. But others may know better. 
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2003 D2 FL S8. Irish Green Pearl/Beige. Solar sunroof, auto-dim mirrors, electric rear seat functions and extended leather. Ski hatch retrofit. Aftermarket reversing camera. DVB-T and XCarlink now removed as redundant.
2016 Volvo V40 T5 Cross Country (4WD) with ALL the toys including adaptive cruise etc. etc. Osmium Grey with Blonde/Charcoal leather interior. Polestar performance "optimisation".  (Even rarer than a D2 S8!) Oh, and a brand new engine at just under 30,000 miles on the factory one! 
Finally: gone, but not forgotten.....
1998 D2 PF S8. Agate Grey/Platinum. Every option (I think) except electric rear seats, Tiptronic steering wheel, ski hatch, towbar & dimming door mirrors.
e.g. Cruise control, NavPlus/TV, Bose, GSM, Xenons, Solar roof, Parking sensors, Alcantara/leather everywhere of course.  (internal dimming mirror added later)
1998 (very early) Ford Focus 1.8 Zetec; ABS/TCS, Heated screen/mirrors, Aircon. Added Auto-dim mirror, Leather seats, Trip computer, Cruise control, OEM Ford SatNav with CD changer.
And before that a lot of Rover 800s, a few oddities, a lovely Triumph Dolomite 1850HL with Overdrive and way back in my schooldays an Austin Seven aka Mini 850!
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