When scrolling the thumbnails, instead of scrolling smoothly, the thumbnails jump or skip several pages up or down. I find this to be frustrating when editing my document via thumbnails because I have to pay extra close attention to verify I'm deleting the correct page or adding a page in the correct slot. With smooth scrolling, I can keep my eye on the sheet of interest when scrolling up or down. (I edit documents a lot with this method) This was one feature I underappreciated about Adobe before I switched to Bluebeam and lost it.