If that is an OE part, I'd be fussing at dealer and MBUSA. That sort of failure is totally unacceptable. MB has done recalls for failing control arms in the past (R107 for instance). How does the other side look?

I would never use an aftermarket control arm. I'd take a used OE control arm over aftermarket.

Have you searched online to see if this type of failure is typical for your model car?

__________________
Respectfully,
/s/
M. Dillon
'87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted
'95 124.131 (E300) "Sapphire", 380k miles
'73 Balboa 20 "Sanctification"
Charleston SC