Found these bits on the drive. Button had been working perfectly

Suspect there might be a third bit but can’t see anything else, or what stops the plastic piece from popping out.

Any fix or new button time - I see a few on eBay or from the usual suspects so I guess they do expire after a two or three decades

Just replaced the motorised catch on my 05 W211 Merc so I expect as much time removing trim without breaking anything as replacing the actual part. Luckily the key opening for the boot on the X300 works fine.