Try switching your CarPlay wallpaper to the all black wallpaper. When I do that, CarPlay has square boarders with no gap. If I switch back to another wallpaper it goes back to rounded edges with black gap. And yes, I tried this in Maps and other apps that had the color go all the way to the edges.
Any idea how to resolve this issue when adding a 2nd vehicle? I changed the script_id to another number. I'm able to get vehicle data in debug menu but widget isn't working.