I sometimes get HTTP 500 response in client and

duplicate key value violates unique constraint "manifest_repository_id_digest"

error in log when pulling from an proxy organization. I've attached complete logs.

Even though I'm not well versed in QUAY source code, I guess it's caused by not handling _ManifestAlreadyExists in data/registry_model/registry_proxy_model.py. Another create_manifest call in data/model/oci/manifest.py is apparently handling it.