Originally Posted by RML

I think what is happening is: When I turn the key to lock the door, the valve in the door switches to the circuit without a leak and therefore the vacuum in the entire system can build up again and has enough pressure to actuate the shutoff mechanism for the engine. I think you are implying that the two circuits are isolated. I do not know. I am just presenting the symptoms and trying to deduce the problem. This is all new to me.

Since you mentioned "a wiper switch shouldn't open the windows", when I move the switch to adjust the passenger side rear view mirror in my 84 300D, the wipers turn on for one cycle. My understanding is that this is a grounding problem, but electricity is not my forte.