I have to tell you, if you applied a 2K primer and allowed it to flash properly, then left it for two days, it is INSOLUABLE and that is all there is to it. It would seal off ANYTHING. If you blocked it and the surface was flat, there were no signs of these "rings" than that is it, done deal. But SOMETHING wasn't done right along these lines.
Leaving the primer to flash and then leaving it to cure after doesn't GUARANTEE that the solvents have all flashed out.
Going back to the "wax and grease remover", if you are using a very slow flashing product it still could be soaking into the substrate. Blowing it with air is only flashing off what you can see, it may be still soaked into the substrate. I don't believe in using any cleaner on the sanded primer UNLESS you KNOW there has been some contamination. If you cleaned it before sanding, it is clean. You do want to use a FAST evaporating cleaner right before paint, but between primer coats it is not nessisary.
You are working on a roof, it is human nature to apply the primer or what ever heavier on a horizontal panel. If you applied your primer heavy, the flash time between coats is a moot point, there still could be trapped solvents. Then sanding and applying more primer in the same heavy coats, MORE solvent. The temp of the surface, the "temp" of the solvents you useing, the air movement in the room, these ALL are factors to solvent flashing as well.
I have to tell you, unless there is a mis-mixed problem where not enough hardener was used or something like that, this
IS a solvent issue. Now, it this
IS a solvent issue than you have to figure out what it is.
You may think you did everything like before, but you may be adding one more factor this time. I call it "alignment of the planets"
That is when you are on the edge of the window on a number of different issues, WHAM, failure. You could be just a little slower on the gun movement, this in it's self isn't a problem. You shot it "Just like before" but this time there is a slightly slower solvent involved, PLUS, it is a little cooler than "before" when you had no problem. These three factors add up to the "planets being aligned" WHAM a failure.
You hardly ever do it "just like before", there is always SOMETHING different, be it temp or SOMETHING.
It could be as simple as applying two or three coats primer, letting it cure for a few hours (did you have at least 60 degrees during that time?) then "breaking it open" with 220 and leaving it til the next day. THEN block it and reprime. That right there could eliminate one of the "planets"
