I have same problem
It appeared after I changed the outer wheel bearing of the front wheel on my sdl. The pulsating starts only on the drivers side when almost at a stop about 80% of the time.
I thought that the ABS sensor or the hub abs ribs were dirty, but cleaning did not help (much).
I then thought that I might have grease on the pads or rotors, so I am hoping that this will go away when the grease burns or gets mixed with brake dust and falls off.
Please post if you figure out what the cause is.
84 300TD - 235k - Farbe "Surfblau" bought at 213k
87 300SDL - 131k - Farbe "PimpGold" bought at 115k
00 Klepper Faltboot Expedition Double