Unfortunately I have the exact same issue.
updating with port 5480 with the ISO still works, but the problem remains
hope that Broadcom wil fix this soon :(
Original Message:
Sent: Sep 23, 2024 11:50 AM
From: Chuck Rohrer
Subject: Can't discard vCenter Upgrade (RDU)
I'm also having this issue at one of our sites with the same error. I upgraded the patches in the manager portal, but in vcenter it thinks it's sill processing the update. Reboots have not resolved the issue. I have found if i mount or unmount the ISO, the vm crashes and the changes do not actually take affect.
Has anyone found a solution?

Original Message:
Sent: Sep 19, 2024 11:45 AM
From: mschmitt-nasuni
Subject: Can't discard vCenter Upgrade (RDU)
Also experiencing this same issue. @XServerCloud did you figure this out?
Original Message:
Sent: Aug 04, 2024 09:42 AM
From: XServerCloud
Subject: Can't discard vCenter Upgrade (RDU)
Several time tried to upgrade vCenter using RDU but anytime didn't succeed.
Just upgraded a plugin and can neither configure target appliance (error with no text) nor discard upgrade workflow.
Got an error:
Structure 'com.vmware.vcenter.lcm.deployment.migration_upgrade.status.task' has a union that is missing a required field 'end_time' for this case