Custom Log in Form issue

I have a custom log in form set up for a specific domain, which works great. When I go to that url, I get the log in form. However, if I log in as a user that does not have rights, it redirects me to the custom log in form for that server. (We have multiple custom log in forms. One for “-All websites/Entire Server”, the rest are set up for specific domains.)

I am not sure why I get redirected to the “Entire Server” custom log in form ONLY if there is an authorization error. If I have an authentication error, it just reloads the proper custom log in form with the “Invalid Username and password” error.

I have even tried other log in forms from other servers that I have this successfully working on, and when I place the log in form on this one server, those also break. Is there some server setting that would cause this to happen?

Thanks!