Hi @bernbeam,
I checked your website and found an error which seems to be caused by an additional <script>
tag which I am not sure where it is triggered from, maybe the custom JS or a plugin:

Also, I see an error regarding the media element blob:
Failed to load resource: net::ERR_FILE_NOT_FOUND
I am not sure the actual cause of the problem, but please follow the steps below which will help to identify the possible issue:
- Test for a plugin conflict. You can do this by deactivating all third-party plugins, and see if the problem remains. If it’s fixed, you’ll know a plugin caused the problem, and you can narrow down which one by reactivating them one at a time.
- Remove custom CSS and Javascript from the options and/or Child Theme and test the case.
- If you’re using a CDN, please clear the CDN’s cache and disable optimization services.
- Test the case by adding a new page and use the Video Element to dd the video in question and if it is working with that element.
- Add a test page and only add one section and use the video as the background of that section and check the case.
kindly get back to us with the result of the steps above and URL/User/Pass of your WordPress dashboard using the Secure Note functionality of the post to follow up the case if you still have problems.