Today I noticed that the driver side door won't lock when I use the key. Usually when I turn the key you can feel a "smooth resistance" when locking and unlocking from the driver's side. Now it feels "hollow".
The door can still be locked and unlocked from the front passenger side and trunk. And I can still lock the door from the driver seat interior when the door is closed .
I have the impression something may be broken within the door handle. I noticed there is a rubber seal behind the door, which leads to a screw that can be taken out to release the handle unit. What should I be looking for when inspecting the door lever?

Also an aside, the door handle on the driver side is getting a little loose. But I presume I may be able to see what the problem is there once the entire unit comes off.

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1998 Ford Escort ZX2 5 speed - 279,000 miles My Daily

1992 Mercedes 300D 2.5 202,000 - Pure junk
2000 Mercedes E320 Black - 136,000 miles - Needs repair

Don't forget to grease the screw and threads on the spring compressor.

Pull the door card and look at the linkage. There is a plug on the back of the door that covers a screw. The screw holds the exterior handle in place. Make sure it is snug.

There's a plastic "lever" going from the key mechanism down to the door lock mechanism. Most likely it has broken off. My SDL had this issue when I first got it due to someone forcing it with a sticky lock mechanism. The key should be very easy to turn in the slot, if it feels stiff, the mechanism needs lubrication and can/will break the plastic lever.

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Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)