Hi - I just completed the Fundamentals of materials and shading, but my renders have strange white artifacts on some of the frames - to demonstrate I have made it into a video, which you can see here - https://www.youtube.com/watch?v=iGSgDXgpBEQ. Anyone any ideas? At lower samples (50), it doesn't seem to be an issue. This is rendered with 500 samples, using all the defaults set in the course download.