In the end it turned out that the Child Lock had not been engaged. I tried the slapping idea but it didn't work, but while driving (and accelerating or braking) I heard a snap noise from the stuck door. Tried opening from outside and it didn't work. But later, just as a thought tried opening from inside and it did work. now it simply doesn't open from outside but does from inside (whatever snapped, caused the block to go away but has disconnected the outside handle) There was a similar problem with the front driver door, can open from inside handle but not from outside. some shaft or connector had snapped and the garage fixed it with a self-tapping screw. So maybe some piece was under stress and was causing the "stuck"ness, and now it has snapped. I guess another self tapping screw may be in order...