This is due to the way ScrollMagic handles sticky/pinned elements. From what I can tell, ScrollMagic does a posteriori detection to determine if a pinned element should be fixed. Basically, it reacts to changes after they happen. So the gap you're seeing is ScrollMagic moving your pinned element back to it's fixed position if you scroll past it. The white is the background color of the body element.   There are a couple ways to prevent this, but I don't know if they will work with ScrollMagic