Unfortunately I have the same problem on chrome and firefox. But I found a little “trick” how to let the browser load all folders.
In general I think the programming of the website is the issue because it doesnt load all folders, it should load after scrolling to the bottom.
WORKAROUND SOLUTION:
I found out if you zoom out to 80% in your browser (tested with chrome and firefox). the folders start to load (also when you scroll to the bottom). Tested it with over 150 folders. With 90% Zoom it doesnt work for me.
So try to zoom out to 80% and scroll down. This should load at least all files. Might be annoying to scroll out all the time.
And I believe this could be fixed easily! Seems like how the website was programmed. 
Hope this helps!
