Flipping Rear Window is driving me nuts - Callign All Experts

[love2speed]

Hi All, I've search this forum high and low and can not seem to find the fix for this so I'm calling all X5 Experts.

Driver Side Rear window only goes down intermittently (ever 20 tries or so), but goes up every time (fail-safe maybe?).

I pulled off the panel and did the following

Tested the switch - OK
Took apart the motor and cleaned brushes and connections - OK
Inspected Cables, tension is good, no fraying - OK
Inspected Regulator no broken clips - OK
Lubricated the hell out of everything

The problem persists, short of trying a process of elimination which involves buying a new motor, regulator, pulley system I'm not sure what to do next?

Any advise is appreciated.