The oc mirror process doesn't detect new heads for operators that were already mirrored once. The oc mirror process doesn't detect new heads but if we list the catalog, new images are listed. 

Client Version: version.Info{Major:"", Minor:"", GitVersion:"4.12.0-202307182142.p0.g3ac49d9.assembly.stream-3ac49d9", GitCommit:"3ac49d9bd7c2193ede794e328dfa1142d7735f2e", GitTreeState:"clean", BuildDate:"2023-07-18T22:43:06Z", GoVersion:"go1.19.10 X:strictfipsruntime", Compiler:"gc", Platform:"linux/amd64"}

Create an initial imageSet configuration to mirror and old image. Then try the process again to update newer images. 

1. Do an initial oc mirror process. I choose two specific operators that were reported by a customer and added a third one at random:

imageset-first-sync.yaml
--
apiVersion: mirror.openshift.io/v1alpha2
kind: ImageSetConfiguration
archiveSize: 4
mirror:
  operators:
    - catalog: registry.redhat.io/redhat/redhat-operator-index:v4.12
      full: false
      packages:
        - name: kubernetes-nmstate-operator
          channels:
            - name: stable
              minVersion: 4.12.0-202302171855
              maxVersion: 4.12.0-202302171855
        - name: amq7-interconnect-operator
          channels:
            - name: 1.10.x
              minVersion: 1.10.9
              maxVersion: 1.10.9
        - name: sriov-network-operator
          channels:
            - name: stable
              minVersion: 4.12.0-202302280915
              maxVersion: 4.12.0-202302280915
storageConfig:
  registry:
    imageURL: registry.testlab.local:5000/oc-mirror/metadata
    skipTLS: true

2. Mirror the first time:

$ oc mirror --config=./imageset-first-sync.yaml docker://registry.testlab.local:5000 --skip-missing --continue-on-error 

3. Ensure the images were mirrored listing the catalog from the internal registry:
$ oc mirror list operators --catalog registry.testlab.local:5000/redhat/redhat-operator-index:v4.12 --package amq7-interconnect-operator
NAME                        DISPLAY NAME                            DEFAULT CHANNEL
amq7-interconnect-operator  Red Hat Integration - AMQ Interconnect  1.10.xPACKAGE                     CHANNEL  HEAD
amq7-interconnect-operator  1.10.x   amq7-interconnect-operator.v1.10.9

$ oc mirror list operators --catalog registry.testlab.local:5000/redhat/redhat-operator-index:v4.12 --package kubernetes-nmstate-operator
NAME                         DISPLAY NAME                 DEFAULT CHANNEL
kubernetes-nmstate-operator  Kubernetes NMState Operator  stablePACKAGE                      CHANNEL  HEAD
kubernetes-nmstate-operator  stable   kubernetes-nmstate-operator.4.12.0-202302171855 

$ oc mirror list operators --catalog registry.testlab.local:5000/redhat/redhat-operator-index:v4.12 --package sriov-network-operator
NAME                    DISPLAY NAME             DEFAULT CHANNEL
sriov-network-operator  SR-IOV Network Operator  stablePACKAGE                 CHANNEL  HEAD
sriov-network-operator  stable   sriov-network-operator.v4.12.0-202302280915

4.- Then, simulating that we need updated operators, we remove the max and min versions:

imageset-second-sync.yaml
---
apiVersion: mirror.openshift.io/v1alpha2
kind: ImageSetConfiguration
archiveSize: 4
mirror:
  operators:
    - catalog: registry.redhat.io/redhat/redhat-operator-index:v4.12
      full: false
      packages:
        - name: kubernetes-nmstate-operator
          channels:
            - name: stable
        - name: amq7-interconnect-operator
          channels:
            - name: 1.10.x
        - name: sriov-network-operator
          channels:
            - name: stable
storageConfig:
  registry:
    imageURL: registry.testlab.local:5000/oc-mirror/metadata
    skipTLS: true

$ oc mirror --config=./imageset-second-sync.yaml docker://registry.testlab.local:5000 --skip-missing --continue-on-error
Checking push permissions for registry.testlab.local:5000
Found: oc-mirror-workspace/src/publish
Found: oc-mirror-workspace/src/v2
Found: oc-mirror-workspace/src/charts
Found: oc-mirror-workspace/src/release-signatures
wrote mirroring manifests to oc-mirror-workspace/operators.1694461638/manifests-redhat-operator-indexTo upload local images to a registry, run:        oc adm catalog mirror file://redhat/redhat-operator-index:v4.12 REGISTRY/REPOSITORY
No new images detected, process stopping

5.- Compare the list of images from Red Hat registry and the internal registry:

$ oc mirror list operators --catalog registry.redhat.io/redhat/redhat-operator-index:v4.12 --package sriov-network-operator --channel stable
VERSIONS
4.12.0-202303081116
4.12.0-202303210718
4.12.0-202305101515
4.12.0-202306261055
4.12.0-202307071529
4.12.0-202307170916
4.12.0-202308231047
4.12.0-202302280915
4.12.0-202304070941
4.12.0-202305262042
4.12.0-202306031829
4.12.0-202307270623
4.12.0-202304190215
4.12.0-202308311226
4.12.0-202301062016
4.12.0-202302072142
4.12.0-202303231115
4.12.0-202303301557
4.12.0-202305022015
4.12.0-202306090942
[root@registry jira_issue]# oc mirror list operators --catalog registry.redhat.io/redhat/redhat-operator-index:v4.12 --package sriov-network-operator
NAME                    DISPLAY NAME             DEFAULT CHANNEL
sriov-network-operator  SR-IOV Network Operator  stablePACKAGE                 CHANNEL  HEAD
sriov-network-operator  4.12     sriov-network-operator.v4.12.0-202308311226
sriov-network-operator  stable   sriov-network-operator.v4.12.0-202308311226

No new images are detected. 

New images should be mirrored.