We were called to diagnose a Benz W211 with the complaint that the steering lock won't unlock and the key won't turn.
After a thorough diagnostic it was found that the steering lock was defective, on Mercedes the steering lock is part of the drive authorisation/immobilizer system and cannot just be replaced without proper programming.
A replacement steering lock could have been ordered but the client did not want to have this problem again, hence we suggested a more robust solution which was to install a steering lock emulator, the client accepted and we programmed the steering lock emulator to the vehicle.
The client was satisifed and has not had such a problem reoccur.