(Feel free to update this bug's summary to be more specific.)
Component Readiness has found a potential regression in the following test:

[sig-arch][Feature:ClusterUpgrade] Cluster should be upgradeable after finishing upgrade [Late][Suite:upgrade]

Significant regression detected.
Fishers Exact probability of a regression: 100.00%.
Test pass rate dropped from 100.00% to 87.20%.
Regression is triaged and believed fixed as of 2025-06-06T16:00:00Z.

Sample (being evaluated) Release: 4.19
Start Time: 2025-06-02T00:00:00Z
End Time: 2025-06-09T12:00:00Z
Success Rate: 87.20%
Successes: 218
Failures: 32
Flakes: 0

Base (historical) Release: 4.15
Start Time: 2024-01-29T00:00:00Z
End Time: 2024-02-28T00:00:00Z
Success Rate: 100.00%
Successes: 625
Failures: 0
Flakes: 0

View the test details report for additional context.

This test unfortunately suffered a major outage late last week, but has failed an alarming number of times since with:

{  fail [github.com/openshift/origin/test/e2e/upgrade/upgrade.go:200]: cluster is reporting a failing condition: Cluster operator monitoring is degraded
Ginkgo exit error 1: exit with code 1}

Sample job runs are those in the report linked above since around Jun 7th. There appear to be about 6.

Example from yesterday:

https://prow.ci.openshift.org/view/gs/test-platform-results/logs/periodic-ci-openshift-release-master-ci-4.19-upgrade-from-stable-4.18-e2e-gcp-ovn-rt-upgrade/1931532175954415616

Intervals show:

source/OperatorDegraded display/true condition/Degraded reason/UpdatingPrometheusFailed status/True UpdatingPrometheus: Prometheus "openshift-monitoring/k8s": SomePodsNotReady: shard 0: pod prometheus-k8s-1: 0/6 nodes are available: 1 node(s) were unschedulable, 2 node(s) had volume node affinity conflict, 3 node(s) had untolerated taint {node-role.kubernetes.io/master: }. preemption: 0/6 nodes are available: 6 Preemption is not helpful for scheduling. [2m49s]