Did, you change these rotors yourself? If not here is a common problem that people who don't know the W126 do and that is they loosen the big bolt in the middle of the hub at the rear thinking that it has to do with the breaks... It doesn't, it holds the axle to the wheel assembly, the mechanic then bangs the rotors off causing seperation between the axle and the hub. You can see the gap when the CV boot becomes gapped from the hub. I made this mistake and had to bang that sucker back on and retighten the whole get-up. Did you or the mechanic remove all rust from the hub? I could be wrong, but check this possibility or you could get killed... The only reason I ever touched that bolt is because a mechanic said to... Big mistake. were the bearings re-greased ? Sometimes too much grease creates false tension when retightening spindle bolts thus under-tightened and bearing failure and what not.. Just thinking out loud.