I posted back in September when this first happened but it cleared itself. It has now happened again and whilst I now know the cause I am stuck as to a fix.
Last Thursday I parked in the Eurotunnel Terminal in France with cases of wine piled on the back seat so, for added security, as well as locking the car I pressed the smaller button to deadlock it so that even if a window was broken the doors would not open. Since then the rear N/S door remains deadlocked. When the car is unlocked the motor can be heard moving in the door along with a satisfying clunk as the lock lever moves to the unlock position. However both inside and external handles remain as if it were still locked.
I have managed to remove the inside panel and can see and touch the lock and see all the linkages from the handles working but I am stumped as to where to go from here. Has anybody had dealings with one of these locks and know how to release it? The cure after that is to never use the deadlock facility, but I have to get the door open first.