Recently bought a Black VW T6 SWB year 221 with a plan to convert it into a camper in a few years. Currently using for work. 2 days ago I spotted a large indentation on the drivers side panel where a window would be fitted. The sun was out and the panel was hot. I got a hose and cooked the panel and the distortion disappeared. Today sun was out again, not as strong but the panel distorted again and when it had cooled down was gone. The van is pkylined inside and has been insulated between the ply and the van body with multifoil. Any ideas ?