After hours of diagnostics from BMW tech, he could not find the problem and eventually ended up clipping the wires that keep blowing the fuse which resulted in no illumination of the back seat window switches, assist module (which I never used) . . . long story short, when I was replacing my HVAC blower I had to remove the center console, and I found a group of wiring that had burned into (the ones for the arm rest phone connections), and then I remembered that Sonic Route 44 coke that the bottom fell out in the cup holders !. I hope this helps in finding your gremlin, it may be in that area.