Personally I'd go with the explanation offered by Jono in the video he posted. The guy in the video, although clearly as loose as a 22mm af spanner on a 10mm af nut head seemed to understand the issue in hand.
Keep a watchful eye on it though.
I trust there is no warranty on the car that you could at the very least have got them to have checked out when it was stuck in reverse?
Shame if not. I must admit it would niggle away with me until I'd found root cause and addressed it in full, can't imagine anything worse than being on holiday/break hundreds or thousands of miles from home and the fault manifesting itself again, hence my recent repairs to the GM, after inspection of the components involved chances are it would have gone another 12-18 months before complete failure of anything but one needs absolute 100% confidence in your car, or I know I do.