Small chemical drip from SS gun

I have a small leak occurring at a self serve with small amount of tire cleaner. What are my processes of elimination? Could it be a check valve in the attic?

Probably some garbage in solenoid or solenoid staying slightly open for some reason.

The check valves in the attic are to prevent high pressure from backfeeding not to stop chemical from leaking. Problem is with either the solenoid or a slight leak in the line causing air to get behind liquid.

You want to remove the solenoid coil and the valve stem and check the inside of the valve for any debris or erosion on the valve seat inside the solenoid valve. Be sure to turn off the air or the power to the solenoid valve or you’ll get a bath of Tire cleaner when you take it apart. A few pictures of what you got are nice.