the problem is the gas tubes in the shock assemblies have discharged and the strut assembly is bad. The only way to fix it is to replace the struts. The assembly may look good but the cartridge in the unit is actually used up. That is the clunking you are hearing. Your MB dealer needs a new tech. This is always miiss diagnosed.

Find a MB indy or a quality dealership .. those retards at your official MB can't even use a toilet paper properly.

my car is doing the same thing and I just bought it 3 days ago. I thought it might just be the E class platform but there is a 3 month 3k warranty that will replace them if needed. As for changing them, if they are set up like my Jag XJR, it's the upper tower bolts, the lower control arm bolt and the air hose. Once the bag deflates, it will just slip straight out. They charged me 75.00 per side to change them but you would have to buy new assemblies. If I hadn't just sent my computer out this morning for a 135 HP increase I would drive my car over some bumpy roads. I'll wait until Wed when the computer is back and in to listen for the noise. I wonder is all the E and CLS has suspension clunks because of the monocock body and the suppression material isn't quite good enough to dampen the noise. I do know my friends 2013 CL550 is dead silent but it was 35k more money and I do know they use more insulation.

what year is your CLS550 and how many miles? How do ball joints go bad so fast? My Jag had 106k miles and the ball joints were never bad just the strut cartridge.