Then your "dealership connections" are feeding you BS. Our '15 GSW had clear evidence of a mouse nest. I thoroughly inspected all of the wiring and only found some missing fabric chewed through, but all of the wire insulation was intact
Where did you hear this? Over the last few years, I have regularly been driving by several huge lots of TDIs near the port facility here in Baltimore, and I can assure you that the cars were packed in so tightly that there was no way they were being maintained or driven on a monthly basis.
Great find! Never assume anything, so just ask. When we got our '15 GSW back in '17, the paperwork included a work order for the pre sale prep. It included tires, alignment, and an oil and filter change. Ours only had 23K miles on it so the brakes were fine. Since yours is now five years old...
There will be codes stored in the ECU. If you can't find anyone nearby who has VCDS, any FLAPS can read the generic OBD codes. If you have that done and report the codes, maybe someone here can help with the diagnosis.