Connection Refused Error when Requesting from a Docker Container to Itself via Nginx Reverse Proxy with UFW Enabled

Question

I have set up a Dockerized environment on an Ubuntu VPS with the following components:

1. A Django container serving a website (example.com).
2. A Nginx container acting as a reverse proxy.
3. All containers are connected to the same network named "prod_net."
4. UFW (Uncomplicated Firewall) is active on the VPS.

My issue is that when I try to make a request from a container to itself via the internet using a command like:

docker exec -it django curl https://example.com/media/image.png --output img.png

I receive a "connection refused" error. However, if I disable UFW, the command succeeds.

My Docker Compose files and Nginx reverse proxy is as follows:

1. Created a Docker Compose file for the reverse proxy and Let's Encrypt companion.

version: "3.7"
services:
    reverse-proxy:
        image: "jwilder/nginx-proxy:latest"
        container_name: "reverse-proxy"
        volumes:
            - "html:/usr/share/nginx/html"
            - "dhparam:/etc/nginx/dhparam"
            - "vhost:/etc/nginx/vhost.d"
            - "certs:/etc/nginx/certs"
            - "/run/docker.sock:/tmp/docker.sock:ro"
            - "./config/my_proxy.conf:/etc/nginx/conf.d/my_proxy.conf:ro"
        restart: "always"
        networks: 
            - "prod_net"
        ports:
            - "80:80"
            - "443:443"
    letsencrypt:
        image: "jrcs/letsencrypt-nginx-proxy-companion:latest"
        container_name: "letsencrypt-helper"
        volumes:
            - "html:/usr/share/nginx/html"
            - "dhparam:/etc/nginx/dhparam"
            - "vhost:/etc/nginx/vhost.d"
            - "certs:/etc/nginx/certs"
            - "/run/docker.sock:/var/run/docker.sock:ro"
        environment:
            NGINX_PROXY_CONTAINER: "reverse-proxy"
            DEFAULT_EMAIL: "[email protected]"
        restart: "always"
        depends_on:
            - "reverse-proxy"
        networks: 
            - "prod_net"
networks:
  prod_net:
    external: true

2- The following is docker-compose for django container and another nginx serving django

version: "3.9"
services:
  nginx_django:
    container_name: nginx_django:
    build: ./docker/nginx
    environment:
      VIRTUAL_HOST:  example.com
      LETSENCRYPT_HOST: example.com
    volumes:
      - .:/var/www/html
      - ./templates/static:/var/www/html/templates/static
    working_dir: /etc/nginx
    links:
      - django
    networks:
      - "prod_net"
  django:
    container_name: django:
    build: ./docker/python
    volumes:
      - .:/var/www/html
      - ./templates/static:/var/www/html/templates/static
    working_dir: /var/www/html
    networks:
      - "prod_net"
networks:
  prod_net:
    external: true
volumes:
  certs:
  html:
  vhost:
  dhparam:

And the following is nginx_django config file:

upstream django {
    server unix:///var/www/html/catalog.sock;
}

server {
    listen      80;
    server_name example.com;

    location /media  {
        alias /var/www/html/media;
        client_max_body_size 1024M;
    }

    location /static {
        alias /var/www/html/templates/static;
    }

    location / {
        uwsgi_pass  django;
        include     /var/www/html/uwsgi_params;
    }

    proxy_connect_timeout   120;
    proxy_send_timeout      120;
    proxy_read_timeout      120;
    send_timeout            120;
    client_body_timeout     120;
}

server {
    listen      443;
    server_name example.com;

    location /media  {
        alias /var/www/html/media;
        client_max_body_size 1024M;
    }

    location /static {
        alias /var/www/html/templates/static;
    }

    location / {
        uwsgi_pass  django;
        include     /var/www/html/uwsgi_params;
    }

    proxy_connect_timeout   120;
    proxy_send_timeout      120;
    proxy_read_timeout      120;
    send_timeout            120;
    client_body_timeout     120;
}

With disabled ufw the problem is resolved. But I expect that, with UFW enabled, I should be able to make requests from a container to itself via the internet without encountering a "connection refused" error