Hi @rmcgn3 👋
That definitely looks like an odd error. My guess is that this error is happening due to some errors in your post editor screen. Could you open your browser console to see if any JavaScript errors are showing up? You can right click anywhere on your browser, click on Inspect Element, and open up the console. If you see any errors, please share them here.
With that said, I strongly suspect this to be a conflict of some sort, and I feel that the error is coming from Radio Buttons for Taxonomies
or Syntax Highlighter for Post/Page HTML Editor
or maybe the SQL Executioner
plugin.
If you wish to do a thorough investigation, please attempt to disable all plugins, and use one of the default (Twenty*) themes. If the problem goes away, enable them one by one to identify the source of your troubles.
If you can install plugins, install and activate “Health Check”: https://wordpress.org/plugins/health-check/
It will add some additional features under the menu item under Tools > Site Health.
On its troubleshooting tab, you can Enable Troubleshooting Mode. This will disable all plugins, switch to a standard WordPress theme (if available), allow you to turn your plugins on and off and switch between themes, without affecting normal visitors to your site. This allows you to test for various compatibility issues.
There’s a more detailed description about how to use the Health Check plugin and its Troubleshooting Mode at https://make.wordpress.org/support/handbook/appendix/troubleshooting-using-the-health-check/.
I hope that guides you in the right direction. All the best!