If you have a pdf with lots of pages and you click on the '/x' button, next to the pagenumber field in the top bar, the last page will be displayed on the right, but the pages thumbnails on the left will not scroll completely down.

This is visible in the demo of the lib and will escalate with more pages. With a 58 pages PDF only half of the 57 pages thumbnail is visible on the left. You have to manually scroll down to see the 58 pages thumbnail.