This is a bit long and convoluted so I'll try condense it:
Took FL2 TD4 SE for fixed towbar fitting. Went to collect, they were having trouble with the rear park sensor giving constant tone. In my absence, they were repeatedly putting the running car in reverse to activate sensors and test (they didn't know about the dash button). They thought it was the bar - I thought electrics (vehicle specific version). We unplugged/re-plugged the electrics interface and the problem righted itself. Great - paid the man and left.

Now the puzzle:
As soon as I drove away, I noticed that the gear shift felt different when selecting 2nd. All the way home, each time I select 2nd it felt as though it wasn't fully selecting. On a few occasions it even fell into neutral. All was perfect before dropping off for the towbar.
What the hell happened? Can them repeatedly selecting reverse perhaps misalign/damage the gear linkage? I'm really stumped as to how this could happen. Looks like it's a dealer trip for me.

sounds like they would have had the clutch down for a extended period, so it might have over heated Former Mod/Member, with the most post & Chicken George Arch nemesis