Never seen this before a week or so ago, noticing it really bad on this site right now.
I go to a thread and read the lastest few posts, hit back button to return to return to unread or todays posts, and "nothing happens", hit it again, and again, and nothing seems to happen. I click and hold the back button and gives me a list of the last pages I have been to in chronological order and find 5-10-20 of that same page listed in my history.
This can happen within a minute or two of entering a specific thread. I do not see it when I am in base forums and subforums, it only happens once I enter an actual thread. It is starting to get crazy, I also notice usually at teh same time that the swirling circle is constantly showing on the tab I am viewing the site in. The "what have you done to your ecoboost today" thread opened up up over 20 entries in my history within <2minutes of me opening it to read it.
Using Firefox 53.0.2