I have footage on a green screen. I need to use part of the footage in front of a black background, a colourful background and a white background. I don't have any issue with the black and colourful ones but when I export my video, the green screen in front of the white background appears with shining stars everywhere. Is there a way to fix this issue? I tried to change the transparency and pedestal first, then try to adjust everything else without success.