I always seem to have major problems trying to run red through my airbrush. Whether it is acrylic, gloss, or flat. Try thinning then thin some more no matter what, airbrush wants to clog. No big deal with armor...we just use spots of pure red, but when building a ship....HULL RED or a model car ..gloss red. I was building a 1950's Mercedes 300 SL Gullwing. Guess I'll back up and paint it blue or black or even Green. Glad my U-boat is dark gray underneath and the Trumpeer 350 scale ships have a red hull color as it comes. Just buy a spray can of red. (YUCK) to do all the other ship bottoms

it happens to me too with the polyscale acrylics.

That's strange, I've never ran across that problem spraying red. I use to clog up spraying flat coats every once in a while, usually solved by simply backflushing, and keeping a brush handy to slap a little thinner on the tip.
I also found that some paints actually do need a larger nozzle than an extra fine or fine nozzle, that I normally use.