my steering wheel got locked while driving what can i do? on 1996 Mercedes-Benz E320

i was trying to sell it and when the buyer was testing it out the steering wheel just got locked and i took out key and its still locked

Asked by for the 1996 Mercedes-Benz E320
We are having this problem right now. The car is at the mechanic's site and they are trying to figure out what actually went wrong. The key will not turn, the steering wheel is frozen, but everything else electronic works in the car. Go figure!!!
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I am having the same or similar problem I have a 1996-e-320.
I have take out the key Cylnder and the steering wheel is still locked.

There is a tumbler where the cylinder goes into and the steering wheel turn a bit but does not un lock .I have no idea any suggestions.

I am assuming there is a button somewhere to release the steering wheel