2012 is T5.1 or GP, or facelift model, it can get confusing, the Germans usually call our T5 a T5.1 and GP models T5.2.

It sounds as if you might have the common door lock actuator fault, usually easiest to replace the whole unit complete, rather than
messing about fixing the micro switches. There are plenty of sellers of those on eBay now, cheaper than genuine, and seem to be
reliable enough. The Brickyard UK has How To's for that job. You can temp lock the rear door, have to take trim panel off,
move lock rods.