Same experience. The tumbler was fine in my 240d. It was something in the mechanism of the steering lock that was binding. I got a nearly new assembly off a guy on eBay for something like $100. I looked into trying to clean up the innards with a file but I gave up for some reason...I think it was hard to open up.

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79 300TD “Old Smokey” AKA “The Mistake” (SOLD)
82 240D stick shift 335k miles (SOLD)
82 300SD 300k miles
85 300D Turbodiesel 170k miles
97 C280 147k miles