Last night, without warning, the key in the driver's side door would turn the tumbler 360 degrees and without resistance. When I went to remove the key, the entire tumbler came out with the key (see picture).

The passenger door tumbler also doesn't work, moving 360 degrees without resistance. That happened a few years ago when I got the car back from a budget paint job. Perhaps the driver's side tumbler problem is related to the same paint job.

Does anybody have tips for me on the theory of operation and how to repair?

This is a 1985 300D.

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