All airbrushes seem to work in one of two ways. They mix the paint and air internally or externally. Even the "Almighty Iwata" does. They all have a pathway for air and a pathway for paint. Iwata included. If either one of these pathways is obstructed, even partially, the airbrush will not operate properly. If there is paint that was allowed to set up in the paint pathway, the thinner that was used to bring it to the proper spraying viscosity will, most likely not disolve this and a stronger solvent will have to be used. I have very small diameter brushes and small diameter music wire for cleaning . The solution to an airbrush that has stopped working is not Iwata, Badger or some other brand of airbrush, but finding the blockage in the one you are having a problem with. It is very possible for every airbrush,even Iwata, to get obstructed in either the air path or the paint path.
I have, over the years, obtained Badger, Paasche, IWATA, a no name gravity feed double action I bought at a swap shop for 5 dollars and they all work fine. I can also make everyone of them quit working, but that would come under the heading of "pilot error". Which means it was my fault and not because of the brand name on the airbrush.
I`m of the opinion that if you get to learn how your airbrush works, how the air goes through and how the paint goes through you will be much more able to take care of the problems that arise.
The reason I mentioned Iwata the way I did is a lot of people seem to think of it as the "Holy Grail" of airbrushes. It is a very fine airbrush, but it can sputter, spit ahd spray to one side just like any other one. It depends on the operator and not the brand name.
Dave