Upgrades from OCP 4.11.9 to the latest OCP 4.12 Nightly builds including 4.12.0-ec.4 will fail.  When the upgrade fails, there are typically two operators that never get upgraded(all others do upgrade to the targeted 4.12.x release):

dns                                        4.11.9                                     True        True          False      11h     DNS "default" reports Progressing=True: "Have 4 available DNS pods, want 5."...
machine-config                             4.11.9                                     True        False         False      14h

The dns.operator details state it is waiting for a 4/5 pods to become available:
# oc describe dns.operator/default
...
Status:
  Cluster Domain:  cluster.local
  Cluster IP:      172.30.0.10
  Conditions:
    Last Transition Time:  2022-10-18T03:21:44Z
    Message:               Enough DNS pods are available, and the DNS service has a cluster IP address.
    Reason:                AsExpected
    Status:                False
    Type:                  Degraded
    Last Transition Time:  2022-10-18T03:21:44Z
    Message:               Have 4 available DNS pods, want 5.
    Reason:                Reconciling
    Status:                True
    Type:                  Progressing

The mcp reports everything is good:
# oc get mcp
NAME     CONFIG                                             UPDATED   UPDATING   DEGRADED   MACHINECOUNT   READYMACHINECOUNT   UPDATEDMACHINECOUNT   DEGRADEDMACHINECOUNT   AGE
master   rendered-master-87fd457ffdaf49d75e62b532c22a9f1d   True      False      False      3              3                   3                     0                      14h
worker   rendered-worker-7fc68009b1facf8724cd952cb08435ff   True      False      False      2              2                   2                     0                      14h

We have performed a large number of the same upgrades, using the same configuration, and while there are times the upgrade succeeds, the large number of results do fail.  This seems to be a timing issue.  

As a current workaround, if we were to recycle the control plane nodes, the upgrade will complete successfully. 

A must-gather log is attached for review.

Tested upgrading to all the following releases:
4.12.0-ec.4
4.12.0-0.nightly-s390x-2022-10-10-005931
4.12.0-0.nightly-s390x-2022-10-15-144437

Moderate to Consistently 

1. Start with a working OCP 4.11.9 Cluster.
2. Perform an upgrade to latest OCP 4.12.x nightly build.
3. Monitor the upgrade status:
   # oc get clusterversion
   —> will state % complete and waiting on dns - which never finishes.
   # oc get co
   —> the dns and machine-config operators will remain at 4.11.9
4. Upgrade will never complete. 

Upgrade will never complete.

Upgrade to the targeted release succeeds.

This upgrade issue occurs for both Connected and Disconnected Clusters.