There is a separate chamber in the vacuum actuator and a separate line to open and close each door. It is possible that there is a leak in the line that locks the door. It is probably yellow with a red stripe. (Yellow with a green stripe unlocks the door).
Sometimes a line will break or slip off the connector or the connecting tube will leak where the line goes into the door. But most likely to fix this you will have to take the panel off the door.
The lines are made of a hard, flexible plastic and they are connected with black rubber connectors. Most problems, they say, are due to a break in the actuator. The next most likely problem is a connector leaking. The hard plastic lines occasionally break.
I have heard that the actuators can be repaired by sliding a couple of condums over the torn bellows and tightening them on with cable ties.
The hard part is asking for especially narrow, yet extra strong, condums.
