I second that. Never had to adjust my focus once set. I also not noticed any uniformity issue.Sounds like a fault. My focus seems to be rock steady. I havent noticed any uniformity issues either. Maybe an issue with a lens element being loose or something.
One thing if the projector is sat too high or too low this could cause it to be Blurred at the top or bottom. If you are tilting it to get it to fill the screen.