Okay, so say I have a Twitch/YouTube/DailyMotion/whatevervideosite up on one display in a Firefox window, and I'm doing some regular browsing in another window on a second display. When I do anything in that second window, any and all video playback will stop, although the audio will continue. As soon as I move my mouse cursor over to the window with the video, the video jumps back to life, skips itself to catch up to the audio, and continues on until I choose to do something in the first window again. Essentially, if I now want to watch a stream or uploaded video, I cannot do anything else with my browser until the video is done. This wasn't happening until 55.0.3, and it seems that even a rollback isn't fixing it (so its buggered something in my registry as well presumably). Any help would be appreciated, because as it stands, I can say goodbye to my off-hours hobby of streaming.