I’ve had the same era of golf as this and the Passat and they both started doing the same thing after about 100K miles, the only thing the doors should do is pressing the unlock button once on the key fob should open the drivers door and twice in quick succession should open all doors (if programmed for this otherwise just once should open all). If they all open at some point and lock then I would say all the door mech’s will be fine and is probably an issue with the central locking and/or wiring. high mileage VW’s of this era are terrible for seals going and water getting into places and causing havoc with electrics all over the place. I would get the central locking system checked and make sure all the other electrics work fine on the car, any other issues with the electrics may lead you to the issue.