Funnily enough, Ive just had the same problem with POR15 paint! I had to weld on a couple of brackets on to my nicely painted chassis, so cleaned an area around the bracket, welded it on and then feathered down the surrounding paint, put on the under coat with out any problem, when I put on the top coat, the feathered edges all started to wrinkle up. My solution was to let it all dry then put another thikish coat of paint on so it pooled with in the wrinkles, then when dry, rubed it down and painted again which seemed to cure the problem. I presume that it is the solvent in the paint that starts to lift a thin edge of the existing paint
