The piece labeled N-020-1 seems to be where the problem is, that brass pin slides up and down inside of it the trigger pushes the brass pin down and opens a slide valve letting air pass threw. On the bottom of the valve is a hex nut that retains that brass center pin I removed it and the pin slides out on the inside of the chamber the brass pin has a second red oring not shown in the diagram when the pin moves the o ring moves with it and it opens or closes a path for the air to flow threw.

 This o ring has grove it is set into and seems to be popping out of the grove and remaining in the closed position while the pin moves freely with out it.

Originally this pin felt spring loaded except when I removed it to inspect as far as I can tell there was no spring unless it was super small and I lost it unknowingly.

When I re assembled it it still functioned for a bit and then I felt the o ring slip again and it stopped.. so right now my airbrush is outta commission untill I can find a replacement part.. modeling today has not gone very successful.

I did switch my paint over to a Tamiya color that I didn't have in the vellejo colors and a lot of the issues I was having didn't occured, which leads me to believe it's a ratio and mixing problem as far as that issue goes. I did notice that the vellejo paint was drying up into film like chunks in the tip and causing problems