Pull-based replication from private docker registry gives "400 Bad Request" when a destination namespace is not given

[imageschool]

(Harbor <-> insecure local private registry)

According to the documents, "If you do not enter a namespace, resources are placed in the same namespace as in the source registry"

With a destination namespace given, the feature seems to work without any issue, however, without a destination namespace the replication fails with 400 Bad Request.