Automatic Window Opens While Driving?

Hello, I couldn't find anything related to this in the search function. Maybe someone here can help! It's about an Audi A6 Avant, model year 2003, chassis code BFC.
During the drive, the rear left window suddenly opened on its own and wouldn't close anymore!
It wasn't until after repeatedly turning the ignition on and off, and waiting for a while, that you could close the window again. This happened at irregular intervals, sometimes two or three times a week.
- A fault scan of the central locking system did not reveal any errors.
-Inspection of the usual fracture points in the door frames, also without success.
- Desperate attempts to switch the window lifter switch, but still no success.
- Replacing the front left switch assembly also did not resolve the issue.
- Replacing the rear left door control module also did not work.
The problem was that the error never occurred when we tried to reproduce it.
Until yesterday, my first test with an LED lamp directly at the window switch on the rear left side showed no measurable potential! It seemed illogical to me, because when I connected the switch, the window immediately went down.
Measurements taken at pin 4 of the window switch using an oscilloscope showed fluctuating voltages between 8 and 10 volts.
Pin 4 is connected to the positive terminal of the front switch assembly (opening signal).
After disassembling the vehicle's interior, the problem was quickly identified.
"On the Avant model, the windshield washer hose that runs to the rear window is routed down along the A-pillar."
The fluid from the vehicle's interior, which was leaking from the clutch, seeped into the cable harness located underneath and into the connector strip in the A-pillar.
After sealing and cleaning the connector, the voltage at pin 4 of the rear left window switch dropped to 0 volts.
However, what I still find amazing is that my LED test lamp and my multimeter didn't show any voltage.
I guess I'll have to get something new.
See you then.