I have used Meyle rotors for the rear of my 03 wagon and they are fine.

The company is German based but these rotors are mostly made in China (mine were and said so on the box, which looks very impressive for a rotor box). So quality control could be a problem.

I still think something is wrong in the re-assemble of the rotors/pads. The caliper carrier bolts should be pretty tight, IIRC. Mercedes suggests to use new bolts but at least thread locker should be used if the old bolts are re-used.