I haven't had that issue but please report it on bugzilla.mozilla.org if you can. Also I would encourage you to try Firefox Beta, currently on version 57, to s

I haven't had that issue but please report it on bugzilla.mozilla.org if you can. Also I would encourage you to try Firefox Beta, currently on version 57, to see if the issue is present there (also that is the version of Firefox the article is talking about).