man, a case of leprosy always sucks. it just happened to me on my racer i'm building. i put down rustoleum primer, let it dry for a few days, sanded it, let it dry some more, then started spraying white dope. damn near the entire plane looked like that almost instantly. my best guess the primer wasn't compatible, and lacquer (dope) reducers are, shall we say, a bit "zesty" compared to enamel thinners. had to sand the entire plane again to make sure ALL of the primer was off, then i put down a really thin coat of silver dope, then a good heavy coat. there were a couple problem spots, so sanded them down, along with the rest of the silver. then i laid down my white, and 2 little spots were still misbehaving.
good enough for a racer! and also i now know not to use that primer.
product compatibility issues really bite!
i've noticed this failure is almost always a compatibility issue on some level, or sometimes simply an adhesion issue from the lower levels being too slick to accept antyhing, so the coating kinda "slides around". polyurethanes and other 2k products tend to get "solvent pops" rather than lifting (assuming you are sticking with a system of coatings and not mixing.....). solvents from lower levels come up and "pop" through the top coats. that's a major bummer as well. it looks almost like a case of acne, and of course never occurs until you're laying on your clear!
if you're using enamels, always try to put the same hardener in the enamel as you are going to be using in your clear to prevent this, soft lines, and also to just get the stuff to dry!