Trying to figure out the difficulties or the bad aspects with the paint zoom is like trying to figure out why the earth is pulled towards the sun. You need to be an expert in physics to really answer that question. Likewise trying to figure out why certain things happen with the paint zoom requires prior understanding of the way a paint instrument that sprays on surfaces works. It is not always perfect the way a paint zoom works but that is not worth complaining for considering how much is comes at.
What a person must realize is that for the money they spend the paint zoom is the best thing in the market and that is what many of the reviews actually point towards. In fact, any complaints or bad paint zoom review against it should be canned because if you want a better instrument then simply invest a lot more than what you would be putting into a paint zoom.