When we use oc-mirror to sync the "registry.redhat.io/redhat/redhat-operator-index:v4.13" image, we found that the digest of the image has changed, oc-mirror added unknown layers for this image.

Client Version: version.Info{Major:"", Minor:"", GitVersion:"4.14.0-202310201027.p0.g68cf97e.assembly.stream-68cf97e", GitCommit:"68cf97ec715ad2d78fb2bac411a118709c191719", GitTreeState:"clean", BuildDate:"2023-10-20T23:48:14Z", GoVersion:"go1.20.10 X:strictfipsruntime", Compiler:"gc", Platform:"linux/amd64"}

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1.Create imageset-config.yml
kind: ImageSetConfiguration
apiVersion: mirror.openshift.io/v1alpha2
storageConfig:
  registry:
    imageURL: dci-mirror-registry.rackg06.local/raven-operators/oc-mirror-metadata
    skipTLS: true
mirror:
  operators:
  - catalog: registry.redhat.io/redhat/redhat-operator-index:v4.13
    packages:
    - name: cincinnati-operator
      channels:
      - name: v1
  additionalImages:
    - name: registry.redhat.io/redhat/redhat-operator-index:v4.13

2.Run command "oc-mirror --config=imageset-config.yml docker://dci-mirror-registry.rackg06.local/operators --skip-cleanup --skip-pruning" to sync image to local registry.

3.pull image redhat/redhat-operator-index:v4.13 from local registry.

local registry image redhat/redhat-operator-index:v4.13 have different
Digest with remote registry.

Expected:
Digest: sha256:73bae297ba51fbd4c2a116b7c08f98dac1532b5e2e96c566d58b10a9f5fc70de
Actual:
Digest: sha256:b6c4642815ef3f29fcd4868a499e73f7bcfff42675093d9a57f9ff0d6310fd33

unknown layers added for image in local registry.

IMAGE          CREATED         CREATED BY                                      SIZE      COMMENT
78c5bac894cb   292 years ago                                                   27.4kB
<missing>      292 years ago                                                   24.2kB
<missing>      292 years ago                                                   0B

The local registry image redhat/redhat-operator-index:v4.13 is same with remote registry.redhat.io.