"Docker Pull" on specific images does not download manifest.json

Symptoms: The Docker image in Artifactory shows up as a folder rather than the logo icon, and Xray is not scanning the image.

Steps to reproduce:

1. On Artifactory 6.8.7, create a remote Docker repository going to Docker Quay ( https://quay.io )
2. Perform a Docker Pull on a specific problem image "coreos/etcd":

docker pull repo.jfrog.team:12069/coreos/etcd
Using default tag: latest
latest: Pulling from coreos/etcd
[...]
Digest: sha256:5b6691b7225a3f77a5a919a81261bbfb31283804418e187f7116a0a9ef65d21d
Status: Downloaded newer image for mill.jfrog.team:12069/coreos/etcd:latest

3. Observe that the folder in Artifactory does not contain a manifest.json:

Index of docker-remote-cache/coreos/etcd/latest
Name Last modified Size
../
list.manifest.json 30-Apr-2019 23:21 6.50 KB
sha256__5f56944bb51c627532324ca0f715de6563c08209fdc5dafa43993fd23652a3e6 15-Jun-2018 17:00 187 bytes
sha256__8bc526247b5c79742e354638a1e33ed2f237c0e7e77adbd0da8fee20085df772 15-Jun-2018 17:00 167 bytes

The Docker image that is pulled works as expected, as the request is served correctly by Artifactory.

However, this problem causes issues with external tools like Xray or the cleanDockerImages User Plugin that rely on the "manifest.json" file.