[Vwdiesel] audi door locks malfunctioning

[Chris Jude]

So in the last couple weeks the door locks on my 1980 Audi 5000s have
started to act up.  Since owning it the vacuum door lock hasn't worked, but
now when i go to manually lock any of the doors, the door in front or behind
the one unlocks.  So I can't lock any of the doors now!
I guess this is a vacuum modulator issue, but can anyone give me some tips
on this?   Unlocked doors in downtown seattle aren't the best idea.

thanks,
chris