First make sure the steering wheel is free to move from side-to-side slightly. If it's holding pressure, inside the column, against the lock, it can cause it to bind. I've literally had to jack a car to unload the pressure (just due to the situation the car was in).

If it doesn't seem to be binding, and depending on where the car is, vibration while turning the key has helped most. I've seen a orbital sander mentioned as a vibration source. When this happened to me, I took a break and gingerly finessed it to turn.

If the key isn't turning, it is a failure of the tumbler, not the column lock.

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Sam

84 300SD 350K+ miles ( Blue Belle )