Hi, Video here: https://streamable.com/jp4if I have this problem where whenever I am watching something in Safari in full screen, randomly a frame from an old video (watched several hours before) would start flickering every time I move the mouse. As you can see in the video, there is a random bright frame that flashes up every single time I move the cursor. Except that the frame is not really random, and I recognise it from a video that I watched earlier this morning. The frame will stop flashing if I don't move the mouse. However, if I have subtitles turned on, the frame will keep flashing as soon as one line of the subtitle disappears, and it will keep flashing indefinitely. This has been happening for years, through several macOS versions. I am using a mid-2012 cMPB 13", running on 10.14.2 Mojave. While the laptop is old, it is running the latest version of macOS, and the fact is that I have had this problem in every version of macOS that ever ran on this. It is a strange issue, and the only solution I found is to restart the mac, but the problem keeps coming back, it happens every day. I have not managed to find a similar issue by anyone, where one frame from a previously watched video is retained and keeps flashing up for hours. Any advice on how I could go about troubleshooting this?