From what I have read, what your talking about is a spot where it looks like the clearcoat is cracking. I had asked a while back what it was, and found out that the clearcoat is detaching from the paint. Yesterday I started to repair some chips in my paint, and decided to repair those spots aswell. Turns out that something got under the paint, and detached it from the primer. When the sun heats it enough, a small amount of water forms, and blisters the paint, cracking the clearcoat. Scraping down to the bare metal and re-layering "primer, color, clearcoat" seems to be the only way to fix it.