Cause: When logging into registry oc sends all requested scopes, which with many images causes the headers sent to registry to be pretty big. Consequence: Some registries have limits on the size of header which might reject big mirroring requests. Fix: Set --skip-multiple-scopes to always true for oc adm catalog mirror which doesn't expose this flag. For oc image mirror users are advised to explicitly set this flag. Result: Mirroring works as expected.