I'm thinking that if the door valve operates by venting the 'unlock' vacuum line in order to allow the doors to lock, then maybe a leak in the 'unlock' line could also cause doors to lock. I guess the leak would have to be similar in size to the amount that would normally be vented. Perhaps this amount would be small enough that while the engine is running, other vacuum functions would not be effected.

I'm not sure exactly how the resorvoir system works, so I wonder if it would be possible to lock/unlock the doors a few times after shutoff even if there was a small leak.

Even if this is true I'm not sure it would explain why the other 3 locks won't engage if they are unlocked manually and then the driver's door is locked.

__________________
Ralph

1985 300D Turbo, CA model
248,650 miles and counting...