I've run my '85 W123 TD thru many a hi pressure was and not had this happen. I do know, from first hand experience that trouble-shooting this electrical problem can be frustrating. The front left/rear right windows are on the same circuit. My first guess is you just blew the fuse, if not then open the door panels and disconnect switches (following the elctrical schematic) until you can isolate the problem area/part.
Also, check the condition of the wiring coming into the rear door from the center pillar...if this is worn from use it could have formed a short.