Originally Posted by MARTINSR
Next possibility, were these the FIRST panels sanded and the urethane primer "healed" before it was painted? Some urethane primers can do this more than others. One primer I use has something crazy like a 4 hour window after sanding to paint, it "heals" that fast. So if it was sanded and sat for a number of days this could be the problem.
I'm sorry, I meant to say they were the FIRST
panels sanded thus they sat longer before the paint was applied. And yes as Henry stated wet sanding helps the ISO's kick even more and often the urethane primer will have a different recoat time if it is wet sanded than dry sanded. Being sorter if it's wet sanded allowing less time to get the top coat on.