We’ve created a few websites using X Theme and Cornerstone and one thing they had in common were background videos for the first x-section. They all work on Surface Pro using various browsers. Recently one website isn’t playing its background video on Surface Pro.
Everything is updated (Theme and Cornerstone) and the URLs of the impacted site is in a private reply following this post.
Would you mind providing a screenshot of what you’re getting from your browser developer’s console? The media library might be failing? And Media isn’t perfectly working on hybrid devices.