Issue with site_url() after upgrade to 4.5.5

In the end I setup a new site with a clean CI install. Ran a diff on all Config, etc files and made any tweaks (nothing related found). Then I started moving my Controllers, Views, etc over in groups until I "broke" the new site. Turned out that the issue was being caused by the auth module CI4-Auth ( https://github.com/glewe/ci4-auth ). Once I moved all my files and disabled all the stuff related to CI-Auth, the problem went away. 
There is a newish release of CI4-Auth that requires CI 4.5. Installed that and took the time to apply my customizations. BAM! All good now. App is finally back to working as it was before the upgrade of CI.
Thanks for your suggestions.