<video id="monitor" preload="none" loop="" muted="" webkit-playsinline="" autoplay="" controls="" style="width: 100%; height: 100%; position:left">
<source src="https://www.elegantthemes.com/videos/previews/build.mp4">
Your browser does not support the video tag.
</video>
Did you resolve the issue? It seems to work for me using the responsive mode setup like you have.
The console logs (which I do not see) indicate a 403 error - which is that there is a permissions error with the files; you will likely just need to change permissions on the web server.
The error is about a video element is having difficulty drawing the little control icons for airplay and picture-in-picture. Technically Safari implements video controls as HTML itself, which is why errors like these show up in the console.
I don't see them myself when testing your site in responsive mode. It probably isn't your error, but just something config-based Safari is choking on.