Wrong url / missing port in storage/app urls

[marcoboehrs]

OC runs on Port 80 behind a reverse proxy (nginx container) with ssl termination which runs on port 8443. I can get all content with https://:8443 but not the images stored in /var/www/html/storage/app/...

In all URLs, except for the storage urls, the port 8443 is present. See attached screenshot from the chrome web developer tools showing the urls.

my oc docker-compose.yml:

version: "3.8"
services:
    web:
        image: "aspendigital/octobercms:php7.4-apache"
        container_name: "octobercms"
        environment:
              - DB_TYPE=mysql
              - DB_HOST=mariadb
              - DB_DATABASE=octobercms
              - DB_USERNAME=octobercms
              - DB_PASSWORD=octobercms
              - CMS_LINK_POLICY=secure
              - VIRTUAL_HOST=<external ip nginx proxy>
              - VIRTUAL_PROTO=http
              - VIRTUAL_PORT=8443                        
        networks:
              - "dmz"
        volumes:
              - /srv/octobercms/plugins:/var/www/html/plugins
              - /srv/octobercms/storage/app:/var/www/html/storage/app
              - /srv/octobercms/storage/logs:/var/www/html/storage/logs
              - /srv/octobercms/themes:/var/www/html/themes

    mariadb:
        image: "mariadb:10.6.2"
        container_name: "database"
        restart: always
        environment:
              MYSQL_RANDOM_ROOT_PASSWORD: 1
              MYSQL_DATABASE: octobercms
              MYSQL_USER: octobercms
              MYSQL_PASSWORD: octobercms
        volumes:
              - /srv/octobercms/mysql/data:/var/lib/mysql
        networks:
              - "dmz"

networks:
          dmz:
              external: true

my nginx docker-compose.yml:

version: "3.8"

services:
    reverse-proxy:
          build: .
          container_name: "reverse-proxy"
          restart: "always"
          networks:
              - "dmz"
          ports:
              - "8443:8443"

networks:
    dmz:
          external: true

nginx.conf server block:

server {
    listen          8443 ssl;
    server_name     <external ip>;

    ssl_certificate         /etc/ssl/certificate.pem;
    ssl_certificate_key     /etc/ssl/certificate.key;

    location / {
        proxy_pass              "http://octobercms:80";
        proxy_set_header Host   $host;
        proxy_cache             off;
    }
}