[tcoradeschi]

Your assumption that this is a wiring problem is likely a good one. I chased similar gremlins in a B5.5 Passat some years back. The culprit turned out to be a broken CANbus wire in the flexible bundle going to one of the rear doors. Took months, on and off. To find it, and about 10 minutes to effect a temp repair to it (solder and shrink tubing).

It’s tedious work, no question about it. Wiring diagrams in the Bentley aren’t totally awful, so use them as best you can.