User blog comment:Rappy 4187/Technical Update: May 20, 2015/@comment-24707114-20150521124544/@comment-126761-20150521131539

It looks like this is due to local custom CSS - if you add ?usesitecss=0 to the URL (which disables local CSS for that pageload), you'll see the issue disappears. I believe the issue lies in, but I am not exactly certain where from my review so far, unfortunately.