Sounds like a bad earth. Check the rear lamps for any corrosion
I had this, fixed it and it's came back within like two weeks. I must have a leak getting into the connectors
So your connectors were showing signs of corrosion ?
Yes, but i cleaned them up but back to how they were. I think the water is geting in from the side of the roof at the back. I tried sliding it back and pulling it up but i didn't want to break it