I'm glad that you've whittled down the cause of the problem. In a way, I'm not surprised because I'm finding more often that some websites have 'preferred' browsers. For example, doing and lodging my tax return online on my country's official government tax website does not work in Edge, so I have to do it in Chrome. But Chrome causes problems with Edge. I had no problems watching YT on Edge until I installed Chrome. YT worked well on Chrome, but frequent buffering (every minute or so) made YT unusable in Edge. Uninstalling Chrome resolved the YT problem with Edge. And my wife has at least 2 websites that need FF. So annoying!