Not a VW but in previous camper we had a serious mice problem. Tried repellent, tried ultrasound devices, sticky pads etc. Caught loads on the sticky pads but I'm afraid ultimately nothing worked. When I took off the internal panels they were nesting in the walls and had eaten through all of the insulation down the one side of the camper. The issue we faced was that the van was stored off-site and despite moving it, the rural (ish) location clearly had a field mouse problem. Dellmassive has a point with the camera to ascertain exactly what it is getting to your wiring. Then trying to deal with that outside of the van plus making the wiring harder to get at I guess. This fills me with dread when we get our camper back