You can double check that browser emulation in registry is correctly set.
Is that a video playback issue or ‘buffering’ ie connection issue?
You’re using webpage widget with embed link to the video on YouTube?
Could try using embed html widget with the script from here and see if it is any different - Autoplay Embedded Youtube Videos
^ it is mostly for android because the embed link with ‘?autoplay=1’ does not work on android, but this script will also work on Windows.