Vacuum Leak in RR Door in W202

[David C Klasse]

I have a leak in the driver's side rear door. Whenever I lock the doors, the leak is not present. But when I UNLOCK the doors, I can hear the air leaking and the pump runs on for atleast 5 seconds before shutting off.

Is this most likely the actuator? I did inspect this problem about 8 months ago, and I was able to wedge something (actually a book of matches!) between the inside of the door frame, and a black rubbery sort of thing (? is this the actuator?) on the inside of the door. It's very hard to see in there to actually see what is loose or leaking.

1. Is it possible that the vacuum line leading to the actuator is loose?

2. Is the black rubber thing inside the door the actuator?

3. How do I inspect in there better? Do I just need to look harder and maybe use a flashlight?

4. Since there is only one vacuum line per door lock (or actuator), then why does it only leak air upon UNLOCKING, but when LOCKING, there is no leak present?

Thanks!