Issue with Advanced GHAD68

Usually dual action top feed airbrushes can drip if the needle doesn't return to the seat properly. That would include the spatter at the start of a pass of spray. Other than that I know nothing about the model of airbrush you listed.

Although:

      I am not familiar with the unit you call out, I will say it sounds like you have a problem like I had with my old DeVillbis fine spray unit. An "O" ring is either split or twisted in the barrel and needs replacing. Probably the one closest to the tip. How old is the unit and what do you clean it with? Once in a while Like a gun, you have to break it down to it's components to refresh the parts and replace the worn ones.