Nginx failure in dockerized container: (111: Connection refused) while connecting to upstream, client

I am running a django app with nginx in a docker container and everything was running perfectly fine up until I rebuild the container. Suddenly I get a 502 (Bad Gateway) error and the logs say

(111: Connection refused) while connecting to upstream, client: 216.245.221.82

I have no idea what changed to be honest and I am a new with nginx. The django/python code should not have changed. I am pulling the latest nginx image so maybe there was a change which doesn't work well with my config. But I tried wit older versions too and get the same error. Maybe my app crashes since there is no port it is listening to? (see screenshot)

I tried adjusting the ALLOWED_HOSTS to ['*'], setting SSL_NO_VERIFY to True and False, still same error. I am out of options.... I don't know how to debug it better. Locally the app works well, so setting debug to True didn't help me.

I just don't know. I am deploying my app on an EC2 instance with nginx in a docker container.

Here are my configs and my compose file:

server {

    listen 443 ssl;
    server_name mywebsite.de;
    client_max_body_size 0;
    charset utf-8;
    ssl_stapling off;
    ssl_stapling_verify off;

    ssl_certificate            /etc/letsencrypt/live/mywebsite.de/fullchain.pem;
    ssl_certificate_key       /etc/letsencrypt/live/mywebsite.de/privkey.pem;


    set $my_host $http_host;
    if ($http_host = "mywebsite.de") {
          set $my_host "mywebsite.de";
    }


    location / {
        proxy_pass http://django:5000;
        proxy_set_header Host $my_host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    }

}

server {
        listen 80 ;
        server_name mywebsite.de;
        return 301 https://mywebsite.de$request_uri;
}
server {
        listen 80 ;
        server_name www.mywebsite.de;
        return 301 https://mywebsite.de$request_uri;
}
server {
        listen 443 ;
        server_name www.mywebsite.de;
        return 301 https://mywebsite.de$request_uri;
        ssl_stapling off;
        ssl_stapling_verify off;

        ssl_certificate           /etc/letsencrypt/live/mywebsite.de/fullchain.pem;
        ssl_certificate_key       /etc/letsencrypt/live/mywebsite.de/privkey.pem;
}

version: '3'

services:
  django:
    build:
      context: .
      dockerfile: ./compose/production/django/Dockerfile
    image: my_website_production_django
    env_file:
      - ./.envs/.production/.django
      - ./.envs/.production/.postgres
    command: /start

  nginx:
    container_name: 'nginx'
    image: nginx:latest
    ports:
      - "80:80"
      - "443:443"
    volumes: ##The following files are found on AWS EC2 instance.
       - /home/ubuntu/nginx-conf/my.conf:/etc/nginx/conf.d/default.conf
       - /etc/letsencrypt/live/mydomain.de/fullchain.pem:/etc/letsencrypt/live/mydomain.de/fullchain.pem
       - /etc/letsencrypt/live/mydomain.de/privkey.pem:/etc/letsencrypt/live/mydomain.de/privkey.pem
    depends_on:
      - django

  redis:
    image: redis:5.0

Happily providing more info or code if needed. Truly desperate and grateful for help. Thank you.