Try to understand why the vertical scrollbar doesn't always appear. Swap 2 different .html files in about.py
I've since learned this problem is dependent on the OS/browser version you're running. It's a problem (scrollbar doesn't appear) in OSX Chrome (Version 73.0.3683.86). But it is/was working on another version of Chrome on Windows. And it was working on MS/Edge and OSX/Safari.