为什么反向动画（）不会马上开火？

I'm using $(window).scroll to animate the top header of my site when scrolling away from the very top of the viewport. The initial condition works fine, with all my animate() effects working. The problem is that when I scroll back to the top of the page, the header doesn't animate back to the original settings (a few times it has, but after a long pause).I'm using $(window).scroll to animate the top h