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.