I've seen this issue in Chrome, Firefox and Safari on Mac with version 8.1.5 installed. I didn't check Windows/IE.
Due to a padding-top of 39px, the vertical toolbar tray can't be scrolled to reveal the last item (which is "Help")
You can see this behavior from the attached gif. It's a bit hard to see from the gif, but if you look closely, there's a menu item "Help" at the bottom before the menu expands, then an attempt is made to scroll down to "Help" again, but the scrolling can't go beyond "Reports", meaning there's no way to access the "Help" item from the vertical sidebar when there's a scroll bar shown.