Dennis, it's a real bummer if the vacuum part of the actuator has gone AWOL.
Obviously I'm not sure of your mechanical DIY skills, however it will involve removing the interior door panel and maybe other items to access the door lock mechanism.
Once removed, inspect the vacuum unit for leaks (cracks, splits etc.)
You may be able to repair this with a hot glue gun, if not double check on that $90 eBay P/N I mentioned in an earlier post, and just replace it.
If your DIY skills aren't up to the above, it will mean a trip to your MB dealer, or to competent independent mechanic.
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