Has anyone else noticed that when in Bookshelf mode and scrolling down the shelf that the scroll is smooth for about ten shelves and then starts jerking as the shelves move up or down the screen? I do not know if it is a refresh issue due to the covers or what but it is distracting. This only occurs in bookshelf mode. If viewing the bookshelf in list mode it does not happen. FYI, I have the 64gb WiFi version and 398 books loaded so far.