NGINX no live upstreams while connecting to upstream

Question

I have Django app, running in Docker container on a host. Also on a host I have Nginx server for this app. Problem that like every 5 - 10 days server not respond and I must restart app container, I don't know what can be wrong.

My Nginx conf:

    upstream django_service {
    server 127.0.0.1:8001 max_fails=0 fail_timeout=10;
}


server {
    listen      443 ssl;
    listen [::]:443 ssl;
    server_name domain.com;
    charset     utf-8;
    client_max_body_size 16M;
    ssl_certificate /etc/letsencrypt/live/domain.com/fullchain.pem; # managed by Certbot
    ssl_certificate_key /etc/letsencrypt/live/domain.com/privkey.pem; # managed by Certbot
#    include /etc/letsencrypt/options-ssl-nginx.conf;

    if ($scheme != "https") {
        return 301 https://$host$request_uri;
    }

    location /media  {
        alias /home/paket/paket2x/var/www/media;
    }

    location /static {
        autoindex on;
        alias /home/paket/paket2x/var/www/static;
    }

    location / {
        proxy_read_timeout 600;
        proxy_pass http://django_service;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header Host $host;
        proxy_redirect http://localhost:8001 https://$server_name;

        access_log /var/log/nginx/paket.access.log paketlog;
        error_log /var/log/nginx/paket.error.log;

    }



}
server {
    listen      80 default_server;
    listen [::]:80 default_server;

    server_name domain.com;
    return 301 https domain.com$request_uri;


}
server {
    listen [::]:443 ssl ipv6only=on; # managed by Certbot
    listen 443 ssl; # managed by Certbot
    ssl_certificate /etc/letsencrypt/live/domain.com/fullchain.pem; # managed by Certbot
    ssl_certificate_key /etc/letsencrypt/live/domain.com/privkey.pem; # managed by Certbot
    include /etc/letsencrypt/options-ssl-nginx.conf; # managed by Certbot
    ssl_dhparam /etc/letsencrypt/ssl-dhparams.pem; # managed by Certbot

    server_name www.domain.com; # managed by Certbot
    return 301 https domain.com$request_uri;



}
server {
    listen      80 ;
    listen [::]:80 ;
    server_name www.domain.com;
    return 301 https domain.com$request_uri;


}

Logs from error.log usually show

no live upstreams while connecting to upstream/Connection refused/Connection reset by peer

Any suggestions what may be wrong?