It is added after setting proxy_server: localhost:8080 as I need to setup a ssh port forward tunnel to access OOD portal. Without this whenever I access localhost:8080 it will be redirected to loclahost automatically.
Turn out you are right. The problem is gone after I kill the ruby process and run /opt/ood/nginx_stage/sbin/nginx_stage nginx_clean --user my_user, just nginx_clean is not enough in my case.
Really appreiciate your help and now our portal just works like a charm.