Sometime within the last couple of weeks I have noticed that elements of YouTube's UI have vanished. Things like the red bar along the bottom of video thumbnails that indicate a video already watched, the video duration on the bottom right of the thumbnails, as well as the 'vertical three dots' ••• menu button underneath thumbnails that contained the "not interested" option no longer appear on the YouTube main page. The three dots menu still exists in the side bar list of recommended videos while actually watching a video, so it's only affecting the main page. I have confirmed that those UI elements work in a different browser and, bizarrely, they seem to work when I use a Firefox private window. This led me to believe that one of my extensions was causing the issue, but even disabling all of them did not bring the missing UI element back in normal browser windows. I have also tried clearing all of my cache, cookies, and site data to no avail. I am on Windows 10 Pro (Version 20H2 OS Build 19042.746) with an up-to-date Firefox (Version 84.0.2 64-bit). Current extensions: BetterTTV, FrankerFaceZ, uBlock Origin, and Facebook Container. Attached image shows the lack of the three dots button on the top normal Firefox window and the presence of that button on the bottom private window. I would appreciate any suggestions as to what may be causing this and possible solutions. Thanks for your time.