nginx proxy pass redirects ignore port
$host
in this order of precedence: host name from the request line, or host name from the “Host” request header field, or the server name matching a request
http://nginx.org/en/docs/http/ngx_http_proxy_module.html#proxy_set_header
proxy_set_header Host $host:$proxy_port;
NGINX Docs | NGINX Reverse Proxy https://docs.nginx.com/nginx/admin-guide/web-server/reverse-proxy/#passing-request-headers