Door locks. My 300D's driver's door lock has been gradually getting harder and harder to operate. I have three keys for the car and sometimes have to try all three before I can get the lock to operate. Sometimes I just give up and crawl over from the shotgun seat.

What is the best solution for this? Can an automotive locksmith "refurbish" the lock to make it work better (lubricants have all failed to help)? Or do I need to go to the dealer and get a new cylinder?

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1994 E500 199/Gray 82k
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