Just had this trouble on my 2012 superb today. Fortunately i managed to open it after a lot of trying... almost all day long. Took the lock away and disassembled it. It actually looked pretty good inside... no corrosion, rust etc. The issue perhaps was related to the fact that the moving part which is plastic slides in the plastic box and runs a bit loose... and there wasn't any lube at that slide. So a little bit of wear and tear on that slide and the plastic part is easy to get stuck. This can be helped if the fast thread is not very well adjusted regarding the position of the moving lock in open position. Anyway i put some silicon oil on the sliding plastics and all works Ok now. Also fyi there is no way for emergency release as long as i can see. There was no release cable etc. The relese pin which is behind a rubber protrusion works fine if it is pushed upwards. But the pin is unreachable because it is behind the metal in the recess. I cut a small channel behind the release pin with the drill and filed it smooth. Now i can reach the pin from below the weel and open the lock in emergency.
