Hi @doublemarvellouscork
Thank you for reaching out.
The 400 Bad Request means that the host server doesn’t understand the URL on your page. It could be a temporary error sometimes, are you still getting the same
Other than that, Often, we see problems occur in combination with another plugin or theme. The fastest way to rule out any conflict is to deactivate all non-Yoast plugins and switch to a standard theme like Twenty Twenty-Two.
Please test this on your development or staging site if you have one. If not, we recommend using the Health Check & Troubleshooting plugin. This plugin has a troubleshooting mode, which does not affect normal visitors to your site.
If you’re unfamiliar with checking for conflicts, we’d like to point you to a step-by-step guide that will walk you through the process: How to check for plugin conflicts