This has happened to my drivers side. I was parked in the corner of a car park and hadn't put my wing mirrors in.. came back to find the drivers side in but the passenger not.. paint on the outside of the drivers side.. someone had hit it..
Its not worked from then it goes in fine but only goes out about half an inch and stops - this happens at the normal speed.. I've to push it out the rest of the way which will finish with a loud pop / click.. I think there are plastic cogs inside which have had teeth broken off... could be a similar case? I'm going to attempt to dismantle and see how this goes so when I do I'll post back!