This happened to me multiple times, and although it doesn't happen every time when it does I have no idea what lead to it except this happens on websites with a lot of images such as web comics or even something like YT with its thumbnails. Suddenly, the scrolling feels very choppy and laggy, as if it was running at a much lower frame rate. I can tell the difference easily as I use a phone with a screen with 120hz refresh rate. I managed to fix it last time by going through the settings, and toggling on and off everything I could. And I have no idea what exactly fixed it. Turning off all the add ons does nothing.