Hello Elise,

Although I think I have provided more than sufficient details, alongwith videos. And was expecting that it could have been checked and resolved without requiring for credentials also.

Anyways, sharing details in the Private section.

We have Not activated any 3rd party Plugin so far. However, you can still deactivate any of the bundled plugin and switch to parent as well.
Nor I have added any custom CSS or other custom code so far in the child theme. Just the demo, as it is.

Please resolve and suggest for each query pointwise.

Regards