4250 Truststore slots tagged 'vasa' could not be migrated to the metadata vdisk.
Explanation
Migration of truststore slots tagged with 'vasa' to the metadata VDisk was attempted but unsuccessful. The first migration attempt happens at upgrade commit time. If it is successful, then no event is raised. If it fails, then the event is raised to allow the user to trigger another attempt.
While the event is unfixed, no maintenance of vasa truststore is possible. This includes adding new certificate bundles, or adding the vasa tag to existing bundles. A vCenter that was registered pre-upgrade, continues to be authenticated by the Embedded VASA Provider while the event is unfixed but new registrations are not supported.