first: maybe this is a problem from odoo or nginx, but would be great if you can help me.

The situation:
LTE Router => pfsense (WAN) => pfsense (LAN) => odoo Server (Ubuntu server 16.04)

The Problem:
When I restart the LTE Router, I cannot connect the webservice over the internal network from the odoo Server with:
https://portal.company.com
Error 502, bad gateway.

Temporary solution:
restart odoo

Now I want to fix this problem.

My Setup in pfSense:
odoo server: receive fixed IP via DHCP (192.168.0.202)
DNS entry to reach the server in local network: https://portal.company.com
Port Forwarding to reach the odoo server also from external

My Setup in nginx:

#worker_processes  1;

#events {
#    worker_connections  1024;
#}

        upstream portal.company.com {
                server portal.company.com:8069 weight=1 fail_timeout=0;
        }

        upstream portal.company.com-im {
                server portal.company.com:8072 weight=1 fail_timeout=0;
        }



        server {
        listen  80;
        server_name portal.company.com;

        location /socket.io {
#               proxy_buffer_size 128k;
                proxy_send_timeout 600s;
                proxy_read_timeout 600s;
                proxy_next_upstream error timeout invalid_header http_500 http_502 http_503;

                proxy_pass   http://127.0.0.1:8068;
                proxy_http_version 1.1;
                proxy_set_header Upgrade $http_upgrade;
                proxy_set_header Connection "upgrade";
                proxy_set_header Host $host;

                proxy_set_header X-Real-IP $remote_addr;
                proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
                proxy_set_header X-Forwarded-Proto https;
                proxy_redirect off;
        }

        location / {
                proxy_redirect off;
                proxy_pass http://portal.company.com;
        }

        location /longpolling {
                proxy_pass http://portal.company.com-im;
        }

        location /web/static/ {
                proxy_cache_valid 200 60m;
                proxy_buffering on;
                expires 864000;
                proxy_pass http://portal.company.com;
        }
 }

Maybe someone can see the problem?

Thank you!