Slow WAN interface - 302/404 issues?

Question

I'm having an issue with a really slow web interface on a self hosted, IN4 install.

It's running on Ubuntu 20.04 LTS and via the LAN IP the app is fast and responsive. However, behind a reverse proxy and served via Cloudflare it's dog slow.

I have the same install on another PC (I'm transitioning to linux) and it works fine behidn the proxy & CF.

Here is my docker-compose.yml

version: '3.7'

services:
  server:
    image: nginx
    restart: always
    environment: 
      - APP_URL=https://URL.co.uk
    volumes:
      # Vhost configuration
      - ./config/nginx/in-vhost.conf:/etc/nginx/conf.d/default.conf:ro

      # Configure your mounted directories, make sure the folder 'public' and 'storage'
      # exist, before mounting them
      -  public:/var/www/app/public
      -  storage:/var/www/app/storage
      # you may use a bind-mounted host directory instead, so that it is harder to accidentally remove the volume and lose all your data!
      # - ./docker/app/public:/var/www/app/public:rw,delegated
      # - ./docker/app/storage:/var/www/app/storage:rw,delegated
    depends_on:
      - app
    # Run webserver nginx on port 80
    # Feel free to modify depending what port is already occupied
    ports: 
      - "8000:80"
      - "4433:443"
    networks:
      - invoiceninja

  app:
    image: invoiceninja/invoiceninja:alpine-4
    restart: always
    environment: 
      - APP_URL=https://URL.co.uk
      - APP_KEY=XXXXXXXXXXXXXXX
      - MULTI_DB_ENABLED=false
      - DB_HOST=db
      - DB_USERNAME=ninja
      - DB_PASSWORD=password123
      - DB_DATABASE=ninja
    volumes:
      # Configure your mounted directories, make sure the folder 'public' and 'storage'
      # exist, before mounting them
      -  public:/var/www/app/public
      -  storage:/var/www/app/storage
      # you may use a bind-mounted host directory instead, so that it is harder to accidentally remove the volume and lose all your data!
      # - ./docker/app/public:/var/www/app/public:rw,delegated
      # - ./docker/app/storage:/var/www/app/storage:rw,delegated
    depends_on:
      - db
    networks: 
      - invoiceninja  

  db:
    image: mysql:5
    restart: always
    environment: 
      - MYSQL_ROOT_PASSWORD=password123
      - MYSQL_USER=ninja
      - MYSQL_PASSWORD=password123
      - MYSQL_DATABASE=ninja
    volumes:
      - mysql-data:/var/lib/mysql:rw
      # you may use a bind-mounted host directory instead, so that it is harder to accidentally remove the volume and lose all your data!
      # - ./docker/mysql/data:/var/lib/mysql:rw,delegated
    networks:
      - invoiceninja

  # THIS IS ONLY A VALID CONFIGURATION FOR IN 4. DO NOT USE FOR IN 5.
  cron:
     image: invoiceninja/invoiceninja:alpine-4
     volumes:
       -  storage:/var/www/app/storage
       -  logo:/var/www/app/public/logo
       -  public:/var/www/app/public
     entrypoint: |
       /bin/sh -c 'sh -s <<EOF
       trap "break;exit" SIGHUP SIGINT SIGTERM
       sleep 300s
       while /bin/true; do
         ./artisan ninja:send-invoices
         ./artisan ninja:send-reminders
         sleep 1d
       done
       EOF'
     networks:
       - invoiceninja

volumes:
  mysql-data:
  public:
  storage:
  # This is needed for letting th cron run correctly
  logo:

networks:
  invoiceninja:

I have checked the logs but there not very populated (perhaps someone can assist in telling me how to enable more logging?) and I have this:

172.31.0.2 -  14/Oct/2020:21:38:52 +0000 "GET /index.php" 200
172.31.0.2 -  14/Oct/2020:21:38:55 +0000 "GET /index.php" 404
172.31.0.2 -  14/Oct/2020:21:39:13 +0000 "GET /index.php" 200
172.31.0.2 -  14/Oct/2020:21:39:16 +0000 "GET /index.php" 404
172.31.0.2 -  14/Oct/2020:21:40:06 +0000 "GET /index.php" 302
172.31.0.2 -  14/Oct/2020:21:40:06 +0000 "GET /index.php" 200
172.31.0.2 -  14/Oct/2020:21:40:10 +0000 "GET /index.php" 404

I suspect the 302/404 is the problem but I don;t know how to dive deeper.

Assistance would be appreciated.

Thanks in advance :)