I had a negative camber problem on a W124 that just wouldnt straighten out... springs, ALL new multilink arms with bushings... yes including the non adjustable camber arms... everything...
So I had a mercedes/bmw body shop that uses sonar measuring systems and a frame machine look at it, and the subframe had actually sagged outta shape. couple of chains and a hydraulic ram later... it was fixed perfectly within specs.
This may not be the problem with yours, but I've seen this problem on other Mercs. that havent been fixed w/ springs,bushings, etc