Can't add application (Err. 500)

Whenever I try to add an application, I get the following:
Error configuring your application: Something went wrong during your request

When I view the Network tab, this appears:

If anyone has any solutions, let me know. Feel like there’s nothing I can do though, given it’s an error 500. Worth noting that I’ve tried multiple devices and networks, with the same outcome. (I know that’s probably not a factor, but I’d rather rule that out just in case)

Come to find out, it’s to do with CORS settings. Whenever I alter any of those, I get an error. I created an application without touching that section, and it worked fine. So the question is now- why can’t I edit CORS settings?