I've had this problem with both Sierra and now High Sierra. When watching videos on YouTube in Chrome, sometimes the video will, from the beginning, have continuous glitches which affect the video (sort of like the video going on and off every 1/2 second) but not the audio part. Most of the time, simply reloading the page gets rid of the problem. I have not had this problem with Chrome on Windows, but I don't watch as many videos on my Windows machine. Anyone else have this problem? Is this is Chrome on macOS problem, a macOS problem, or a hardware problem? Is there a fix for it? Thanks.