The brake is something I have had some bad moments with. With my ’64 FHC I had a complete brake failure and nearly run into a bus after a descent. I was scared to death and did not want to touch the car anymore. But as I always want to fix it, I did a research.  Found out that one wheel cylinder was sized up and the reason I found here. Basically, the DUNLOP brake cylinder like to size up from corrosion caused by the water absorbed from the brake liquid and after standing in there for a while. 

Dunlop-Bremsprobleme beseitigen | Beitrag | Mercedes-Benz Oldtimer-Newsticker