If you still have a problem, check out my problem W124 Central Lock Puzzle
regarding a similar issue. What I found out later with the W124 was the A/C water drain hoses (one on each side) of the passenger compartment will disintegrate on an older vehicle(1987) and water will flow into the floor panels and run down the wiring harness. In my case, this caused the X48F connector to corrode and only one actuator had enough current to operate. Just a thought!
1987 300D 185Km
2001 CLK 430 Convertible 27Km