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;
	}
}