These so called problems are actually nothing more than limitations that the paint zoom has to have because without them it cannot literally function flawlessly as it does. First up is the issue with its limited capacity. The simplest explanation for those who complain is that the paint zoom is supposed to be a versatile device meant for use by anyone including housewives. Obviously, this means that it needs to be lightweight and providing a higher tank capacity somehow does not fit well into this equation.
Next problem on the list is its tendency to paint over the surface it is targeted at. That shall happen regardless of the brand of paint sprayer you use. Even industrial grade machines suffer from this problem. The way to overcome this issue is to stick tape or newspaper over surfaces you do not want paint on. Otherwise you will always end up with paint all over the place.