Ahh ok.
So this afternoon I noticed a wet patch in the back corner of my van. After doing some checks, I have discovered that I have water entering the vehicle internally into the side voids.
The voids are soaked and when I pulled the matting back, the floor area was also wet.
My guess is that it’s coming through the bolt holes for a roof rack. I’ve siliconed and tightened them this evening and pulled the internal panels off slightly to allow for air flow.
Im thinking.. and it’s a long shot, that this may be the reason why my mirror is playing up. Moisture on the connections playing havoc…
Anyway it may pay for you to check your van for any water ingress just to rule it out.
As I said, its a long shot but worth a look.