Failed to load dialog parameters - The dialog parameters are not consistent, please try to reopen th

Hello,

I have a Kentico 12 instance installed and am getting an error when trying to open the Add Sites option on the CSS stylesheets. The error does not show anything in the event log but comes back as a 500 error in the search console.

What could be the cause of this error? This is consistently happening. I've tried restarting the application, clearing my cache, and clearing the kentico cache.

Thanks, Jeff