Proxy Docker Hub Through Nexus

I am trying to proxy SUSE Registry and Docker Hub Registry through our Nexus Repository Manager.

In addition we have one internal Docker repository.
I have created a docker group repository, that combines all three.

We are able to access our own docker images from the internal docker repository, but it fails to pull any images from Docker Hub and SUSE.

SUSE: https://registry.suse.com
Allow anonymous docker pull
Docker Index: Use proxy registry

Docker Hub: https://registry-1.docker.io
Allow anonymous docker pull
Docker Index: Use Docker Hub

Pulling from SUSE images through the group:

docker pull nexus.company.com:38380/suse/sle15:15.2
15.2: Pulling from suse/sle15
f3d2df4815db: Pulling fs layer
error pulling image configuration: unknown blob

This works: docker pull registry.suse.com/suse/sle15:15.2

Pulling from Docker Hub images through the group:

docker pull nexus.company.com:38380/opensuse/leap:15.2
Error response from daemon: manifest for nexus.company.com:38380/opensuse/leap:15.2 not found: manifest unknown: manifest unknown

This works: docker pull opensuse/leap:15.2

Any idea what the problem might be here?
Our Nexus uses HTTPS.