Do you have a second key? It might not be the lock, but rather a worn key.

My "old" key would frequently stick in the door lock and ignition months ago. I tried my spare key, which is newer, and no problems.

I keep both keys on my fob. The new one always turns silky smooth. If the old key sticks I remove it, turn it upside down and it then it works too, so in my case it is a key wear issue.

If you have a spare key, or can get a new one made, try that before assuming the ignition tumbler is faulty -- especially if the key also sticks in the door locks, since it is unlikely all of them will fail simultaneously.

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2008 E350 4matic / Black/Anthracite

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Gone but not Forgotten:
2001 E430 4matic, 206,xxx miles, Black/Charcoal
1995 E320, 252,xxx miles, Black/Grey
1989 260E, 223,00 miles, Black/Black

Have tried the second key once. But i will give it another try!

FINALLY! After drilling it down to crumbles I managed to use a screwdriver and make it turn!!
Ill put up some pics and stuff later

klann makes a tool which removes the broken switch when it's locked. Designed for W124 chassis so you don't mess with all the problems and time with dash work.

Got any photo of that tool?