Ball Joint Failure

[Matsalleh76]

[Rouven036]

the reason is like you have discovered ,the cheap shit ball joints.maybe mercedes parts are not as cheap as these you have used , but there is a reason for the higher price.
axle-,suspension-,brake-,steering parts etc. are safetyparts and you should never ever save money on this place because your life and the life others could hang on it.
of course when your ball joints are worn out,there is often an squeaking and groaning noises while turning the steeringwheel.if you ignore it a while it could be that the pin would be pulled out of the socket when the steering is in full angle.
if you use parts with higher quality and mount them correctly , then the liftime of the ball joints will be 100tkm or longer,debends also on the roads.
i think,if you check the ball joints every 20tkm it would be enough.there is also a special tool from mercedes available to measure the ball joints when the care is standing on the wheels.