Fwiw I just went through this on my 05 wagon. Broken wires in the top of the tailgate just inside the body of the car. Luckily my guy was able to pull them out enough to fix it without taking down the headliner.
Backstory:
My original motor died so a used motor was put in by a local shop I use sometimes, and then intermittent wouldn't work. They then replaced the switch on the wiper stalk and checked fuses but no luck. They told me it was the BCU but I didn't believe that they actually checked the wiring in the roof, so I took it to my regular shop and they immediately found that broken wires were the cause.
Now I don't have to obsessively play "park the wiper so it's not uneven" anymore.....