The browser fetch for api calls fail with
"Failed to execute 'fetch' on 'Window': Request cannot be constructed from a URL that includes credentials: /api/server"
If you then remove the auth and open http://localhost:9080/admin/ again, it will work as the browser already knows the basic auth header for the host.
When passing the basic auth as part of the URL,
For example, with http://admin:e10adc3949ba59abbe56e057f20f883e@localhost:9080/admin/
The following happens...
It seems that the API calls fail to start.
The browser fetch for api calls fail with
"Failed to execute 'fetch' on 'Window': Request cannot be constructed from a URL that includes credentials: /api/server"
If you then remove the auth and open http://localhost:9080/admin/ again, it will work as the browser already knows the basic auth header for the host.