eh...What is the difference between power and express Up/Down?
Whatever the difference is; the malfunction cannot be caused by a fuse, since the fuses do power more as one window.
The system is controlled by a comfort relay and a relay that combines the power roof and power windows (that is if the 95 S-class electrics are the same as the 95 C-class electrics...mercedes changed the C-class (and other models) electrical systems in 1997).
I think that the problem can be found in the motor or wires of the rear window/door or in the relay that controls the windows and roof..
If the S-class was way ahead of the C-class and has the same electrical system as is used in the late "97 and later C-class, I think the relay in the mentioned door will be the one causing the problem (the later C and E classes have a relay in every single door for the powered parts; maybe the 95 S-class had that as well).
just a thought, greetingz,
with a minor 600+k