From years of panel beating/painting it's usually caused via a chemical reaction between products ie old paint/primer/clear to new. This is why most painters will use a 2k primer before painting and clearing. Obviously you don't want to prime your lovely Playfield so the risk for fish-eye is high. For future reference two drops of eliminator in the gun and load it up, turn on the oven or infrared and come back to glass! Either way your fine, let it dry, block it back and load it up.

Fyi don't use 2pak in that booth and don't use it with out the proper 2pak mask. You will take 30 years off your life spraying 2pak with no mask. There's a reason why a proper certified booth costs $40,000+

Feel free to spray enamel, lacquer, dulon etc in that sweet home made booth