During an upgrade of a cloud from Stein to Train, there is a migration which adds the `hidden` field to the database. In that migration, it was assumed that it does not backfill all of the columns. It was discovered that when the number of instance records in the db exceeds ~ 300K the migration can fail to set all the fields resulting in some instnaces are no longer viable when you do openstack server list. This was reported and tracked upstream by https://bugs.launchpad.net/nova/+bug/1862205 and addressed upstream by https://review.opendev.org/#/c/706582/ This bugzilla tracks any downstream work that needs to be completed to ensure this is highlighted in release notes and fix in the next oap 16 async.
Since the problem described in this bug report should be resolved in a recent advisory, it has been closed with a resolution of ERRATA. For information on the advisory, and where to find the updated files, follow the link below. If the solution does not work for you, open a new bug report. https://access.redhat.com/errata/RHBA-2020:2154