Upgrading cluster stuck at "downloading update" phase

Issue

• OCP upgrade to 4.6.32 stuck at "Downloading update"

$ oc get clusterversion
NAME     VERSION  AVAILABLE  PROGRESSING  SINCE  STATUS
version           True       True         4m31s  Working towards 4.6.32: downloading update

• Hundreds of pods scheduled in Openshift-cluster-version namespace for the upgrade job and in Failed state

$ oc get pods|grep Failed|head
version-4.6.29-2hpbq-5gjj2                0/1    Failed   0         5d
version-4.6.29-2hpbq-6qr8f                0/1    Failed   0         5d
version-4.6.29-2hpbq-9ptbq                0/1    Failed   0         5d
version-4.6.29-2hpbq-s42q8                0/1    Failed   0         5d
version-4.6.29-2klh8-gc82f                0/1    Failed   0         5d
version-4.6.29-2klh8-kbp9n                0/1    Failed   0         5d

$ oc get pods|grep Failed|wc -l
4362