Just been watching a flick on the projector, and I have noticed a small grey circle bottom left of the screen which appears when the projector is playing something very dark, or if it has no input on a certain mode (like AV1 mode but not having anything turned on if you know what I mean). I first thought it was light reflecting on the screen, but its not as when I move the projector, the circle moves with it. I tried cleaning the lens with a glasses cleaning cloth, but that hasnt helped. Any ideas? Thanks.