Why does docker pull from private Docker registry using nginx SSL reverse proxy work on registry host, but not remote host?

Why does docker pull from a private Docker registry using an nginx SSL reverse proxy work on registry host, but not remote host?

Successful docker pull From registry host:

admin@vps58622:~/docker-registry$ docker pull www.opessolutions.com:5043/busybox
Using default tag: latest
latest: Pulling from busybox
Digest: sha256:6757d4b17cd75742fc3b1fc1a8d02b45b637f2ac913ee9669f5c2aed0c9b26ba
Status: Image is up to date for www.opessolutions.com:5043/busybox:latest

Docker logs:

nginx_1     | 158.69.212.126 - - [25/May/2016:16:41:54 +0000] "GET /v2/ HTTP/1.1" 401 195 "-" "docker/1.11.1 go/go1.5.4 git-commit/5604cbe kernel/4.4.0-22-generic os/linux arch/amd64 UpstreamClient(Docker-Client/1.11.1 \x5C(linux\x5C))" "-"
registry_1  | time="2016-05-25T16:41:54Z" level=info msg="response completed" go.version=go1.6.1 http.request.host="www.opessolutions.com:5043" http.request.id=4302d195-a4b4-4dfb-93b3-802ab6cacf28 http.request.method=GET http.request.remoteaddr=158.69.212.126 http.request.uri="/v2/busybox/manifests/latest" http.request.useragent="docker/1.11.1 go/go1.5.4 git-commit/5604cbe kernel/4.4.0-22-generic os/linux arch/amd64 UpstreamClient(Docker-Client/1.11.1 \\(linux\\))" http.response.contenttype="application/vnd.docker.distribution.manifest.v2+json" http.response.duration=6.762288ms http.response.status=200 http.response.written=711 instance.id=701faf44-22ad-4386-9305-46a0167b95c8 version=v2.4.0 
registry_1  | 172.17.0.3 - - [25/May/2016:16:41:54 +0000] "GET /v2/busybox/manifests/latest HTTP/1.0" 200 711 "" "docker/1.11.1 go/go1.5.4 git-commit/5604cbe kernel/4.4.0-22-generic os/linux arch/amd64 UpstreamClient(Docker-Client/1.11.1 \\(linux\\))"
nginx_1     | 158.69.212.126 - derek [25/May/2016:16:41:54 +0000] "GET /v2/busybox/manifests/latest HTTP/1.1" 200 711 "-" "docker/1.11.1 go/go1.5.4 git-commit/5604cbe kernel/4.4.0-22-generic os/linux arch/amd64 UpstreamClient(Docker-Client/1.11.1 \x5C(linux\x5C))" "-"

Failed docker pull from remote host:

derek@derek-lubuntu:~/Projects/docker-library$ docker pull www.opessolutions.com:5043/busybox
Using default tag: latest
Pulling repository www.opessolutions.com:5043/busybox
Error: image busybox not found

Docker logs:

nginx_1     | 66.171.168.90 - - [25/May/2016:16:42:05 +0000] "GET /v2/ HTTP/1.1" 401 195 "-" "docker/1.11.1 go/go1.5.4 git-commit/5604cbe kernel/4.4.0-22-generic os/linux arch/amd64 UpstreamClient(Docker-Client/1.11.1 \x5C(linux\x5C))" "-"
nginx_1     | 2016/05/25 16:42:06 [error] 7#7: *5 open() "/etc/nginx/html/v1/_ping" failed (2: No such file or directory), client: 66.171.168.90, server: www.opessolutions.com, request: "GET /v1/_ping HTTP/1.1", host: "www.opessolutions.com:5043"
nginx_1     | 66.171.168.90 - - [25/May/2016:16:42:06 +0000] "GET /v1/_ping HTTP/1.1" 404 169 "-" "docker/1.11.1 go/go1.5.4 git-commit/5604cbe kernel/4.4.0-22-generic os/linux arch/amd64 UpstreamClient(Docker-Client/1.11.1 \x5C(linux\x5C))" "-"
nginx_1     | 2016/05/25 16:42:06 [error] 7#7: *6 open() "/etc/nginx/html/v1/repositories/busybox/images" failed (2: No such file or directory), client: 66.171.168.90, server: www.opessolutions.com, request: "GET /v1/repositories/busybox/images HTTP/1.1", host: "www.opessolutions.com:5043"
nginx_1     | 66.171.168.90 - - [25/May/2016:16:42:06 +0000] "GET /v1/repositories/busybox/images HTTP/1.1" 404 169 "-" "docker/1.11.1 go/go1.5.4 git-commit/5604cbe kernel/4.4.0-22-generic os/linux arch/amd64 UpstreamClient(Docker-Client/1.11.1 \x5C(linux\x5C))" "-"

Notice that in the failed attempt, nginx doesn't forward the request to Docker Registry. It also seems to translate the Docker Registry API v2 request into a v1 request.

nginx/registry.conf

upstream docker-registry {
  server registry:5000;
}

## Set a variable to help us decide if we need to add the
## 'Docker-Distribution-Api-Version' header.
## The registry always sets this header.
## In the case of nginx performing auth, the header will be unset
## since nginx is auth-ing before proxying.
map $upstream_http_docker_distribution_api_version $docker_distribution_api_version {
  'registry/2.0' '';
  default registry/2.0;
}

server {
  listen 443 ssl;
  server_name www.opessolutions.com;

  # SSL
  ssl_certificate /etc/nginx/conf.d/domain.crt;
  ssl_certificate_key /etc/nginx/conf.d/domain.key;

  # Recommendations from https://raymii.org/s/tutorials/Strong_SSL_Security_On_nginx.html
  ssl_protocols TLSv1.1 TLSv1.2;
  ssl_ciphers 'EECDH+AESGCM:EDH+AESGCM:AES256+EECDH:AES256+EDH';
  ssl_prefer_server_ciphers on;
  ssl_session_cache shared:SSL:10m;

  # disable any limits to avoid HTTP 413 for large image uploads
  client_max_body_size 0;

  # required to avoid HTTP 411: see Issue #1486 (https://github.com/docker/docker/issues/1486)
  chunked_transfer_encoding on;

  location /v2/ {
    # Do not allow connections from docker 1.5 and earlier
    # docker pre-1.6.0 did not properly set the user agent on ping, catch "Go *" user agents
    if ($http_user_agent ~ "^(docker\/1\.(3|4|5(?!\.[0-9]-dev))|Go ).*$" ) {
      return 404;
    }

    # To add basic authentication to v2 use auth_basic setting.
    auth_basic "Registry realm";
    auth_basic_user_file /etc/nginx/conf.d/registry.htpasswd;

    ## If  is empty, the header will not be added.
    ## See the map directive above where this variable is defined.
    add_header 'Docker-Distribution-Api-Version' $docker_distribution_api_version always;

    proxy_pass                          http://docker-registry;
    proxy_set_header  Host              $http_host;   # required for docker client's sake
    proxy_set_header  X-Real-IP         $remote_addr; # pass on real client's IP
    proxy_set_header  X-Forwarded-For   $proxy_add_x_forwarded_for;
    proxy_set_header  X-Forwarded-Proto $scheme;
    proxy_read_timeout                  900;
  }
}

docker-compose.yml

nginx:
  image: nginx:1.9
  ports:
    - 5043:443
  links:
    - registry:registry
  volumes:
    - ./nginx:/etc/nginx/conf.d:ro
registry:
  image: registry:2
  ports:
    - 127.0.0.1:5000:5000
  environment:
    REGISTRY_STORAGE_FILESYSTEM_ROOTDIRECTORY: /data
  volumes:
    - ./data:/data