Embedding Scheduled Livestream Defaults to 4×3 on Self-hosted

I’m trying to resolve an issue where WordPress uses 4×3 formatting for scheduled livestreams on YouTube under certain circumstances. When creating a new scheduled stream on YouTube, there are two options: “Create New” or “Reuse Settings”. If reusing settings, it will let you choose a previous broadcast as the starting point. For reference, all our broadcasts are in 16×9.

Sample YouTube Scheduled streams
Create New: https://youtu.be/qZ2vczDt_RQ
Reused: https://youtu.be/yC13jv1YVSI

Pasting these two links into WordPress results in the “new” one being 16×9 while “reused” is 4×3. If I manually change the “Additional CSS Classes” on the block tag, I can force 16×9 but making this change from the default that WordPress fills in:

wp-embed-aspect-4-3 wp-has-aspect-ratio
wp-embed-aspect-16-9 wp-has-aspect-ratio

Also of note: WordPress does not save the custom CSS class change if you make any changes to the block or edit the post again in the future. Both links will appear in 16×9 on YouTube if you click through. But only “new” scheduled streams appear in 16×9 when embedded. Once the livestream is over, it pastes correctly into WordPress as 16×9.

The problem does not seem to occur on WordPress.com hosted accounts. I have tried:

* Two self-hosted blogs with two different themes.
* Deactivating all plugins.
* Changing to default 2021 Theme.

Any leads on what I can try to correct the problem or isolate a potential bug, I’m all ears. I have a staging site where you can see this in action, linked above.

The page I need help with: [log in to see the link]