[Collabora] Configuration with docker-compose

Ok, that sounds to work now, but only when the collabora url within Nextcloud settings is set to the collabora website external address (<office.domain.tld>). When it is set to the local url http://collabora:9980, I have the following error:

Collabora Online unknown error: cURL error 52: Empty reply from server Please contact the “http://collabora:9980” administrator.

When using the external url the access is pretty long and I have latency navigating through the documents, Hope that could be solved if I succeed to connect through the local url. If someone could help me understand, that would be nice.
Below is my configurations. the reverse proxy and nextcloud configuration are broken down in two docker-compose.yml:

version: '2'

services:

  proxy_nginx:
    image: jwilder/nginx-proxy
    container_name: proxy_nginx
    privileged: true
    restart: always
    ports:
      - "80:80"
      - "443:443"
    volumes:
      - ./proxy/certs:/etc/nginx/certs:ro
      - ./proxy/vhost.d:/etc/nginx/vhost.d
      - ./proxy/conf.d:/etc/nginx/conf.d
      - ./proxy/html:/usr/share/nginx/html
      - /var/run/docker.sock:/tmp/docker.sock:ro
    networks:
      - front

  proxy_letsencrypt:
    image: jrcs/letsencrypt-nginx-proxy-companion
    container_name: proxy_letsencrypt
    privileged: true
    volumes:
      - ./proxy/certs:/etc/nginx/certs:rw
      - /var/run/docker.sock:/var/run/docker.sock:ro
    volumes_from:
      - proxy_nginx

networks:
  front:
    external:
      name: proxy-ssl

and

version: '2'

services:

  app:
    image: wonderfall/nextcloud
    privileged: true
    links:
      - db
      - collabora
    environment:
      - UID=1000
      - GID=1000
      - UPLOAD_MAX_SIZE=10G
      - APC_SHM_SIZE=128M
      - OPCACHE_MEM_SIZE=128
      - CRON_PERIOD=15m
      - VIRTUAL_HOST=<cloud.domain.tld>
      - VIRTUAL_NETWORK=proxy-ssl
      - VIRTUAL_PORT=8888
      - LETSENCRYPT_HOST=<cloud.domain.tld>
      - LETSENCRYPT_EMAIL=<admin@domain.tld>
    volumes:
      - ./data:/data
      - ./config:/config
      - ./apps:/apps2
    networks:
      - front
      - back

  db:
    image: mariadb:10
    restart: always
    privileged: true
    environment:
      - MYSQL_ROOT_PASSWORD=<password>
      - MYSQL_USER=user
      - MYSQL_DATABASE=db
      - MYSQL_PASSWORD=<password>
      - TZ="America/Chicago"
    volumes:
      - ./mysql:/var/lib/mysql
    networks:
      - back

  redis:
    image: redis
    networks:
      - back

  collabora:
    image: collabora/code
    expose:
      - 9980
    cap_add:
      - MKNOD
    environment:
      - domain=<cloud.domain.tld>
      - VIRTUAL_HOST=<office.domain.tld>
      - VIRTUAL_NETWORK=proxy-ssl
      - VIRTUAL_PORT=9980
      - VIRTUAL_PROTO=https
      - LETSENCRYPT_HOST=<office.domain.tld>
      - LETSENCRYPT_EMAIL=<admin@domain.tld>
    networks:
      - front

networks:
  front:
    external:
      name: proxy-ssl
  back: