Hi, just a piece of information of my 2012 W246 B180 Mercedes.
Wipers started to behave randomly, they stopped working and after waiting for some time, they worked again. Then the motor started to slow down. Even with full speed it was pretty slow. Then they just stopped and did not move anymore. Went for local garage to read the diagnostics and saw the motor gave fault code. Obviously merc had tied the motor to the wiper arms, and the spare part was 398euros. Luckily it was very easy to switch and took only like an hour.