- 1. You have tried using 2 different guns. Are they both from HF? Have they been cleaned with brushes and lacquer thinner?
2. The brand of paint is Summit. Are you using a clear coat or just single stage urethane paint?
3. The primer doesn't seem to have the same issue? The primer is epoxy made by Summit also?
If you are still using the same lacquer thinner, I would junk it and use fresh thinner.
Since your hose was contaminated from the line being hooked up wrong, I would buy a new air hose and use it only for shooting paint. Save the other one for air tools. You can get a decent Goodyear brand hose from HF for $20. I usually use the "red" 25 foot hoses the local tool store sells. Having a shorter 25' hose also helps not having it tangle up or lug the hose around the car.
This time:
When you clean the gun, let the lacquer thinner sit in the cup 30 mins or so. It will help loosen anything that is really stuck to the sides of the cup and down through the fluid passage.
After the gun has sat with thinner, break it back down and clean all of the parts with a gun brush and new lacquer thinner. I usually do this over a mixing cup so I can swish the parts around in the cleaner and let them soak while I'm brushing each part.
Lay out a shop towel and set the parts on the towel while you are cleaning the gun body. Wipe everything down again with a new dry shop towel.
Assemble the gun and shoot lacquer thinner through it to see how it is spraying and remove any stray residue that might have been stuck in the passages.
Now load your paint into the gun and see if you still see the fish eyes forming on the sides of the cup. If you don't get any fish eyes in the cup, try spraying a test panel that has been prepped and cleaned with wax and grease remover. If you don't have any problems, try shooting another panel or your project and see if the problem is fixed.
Also, when you are switching materials or getting ready to clean the gun, it helps to percolate some thinner through the gun to flush it out.
How to percolate clean a spray gun: