This is effectively the same issue that was reported here:
It looks like we have the same issue with the
4.12.2 release that we had with the
4.12.1 release with Tag Manager.
Because the update file for the
4.12.2 release was not renamed to a
4.12.2 update file anyone who was already on
4.12.1 and updated to
4.12.2 would still have the same issue.
To get the updates to run they would need to set their version for Tag Manager to
4.12.0 and then run core:update again.
To properly fix it for everyone we would need to rename the update file to something like
4.12.3-b1.php and then release 4.12.3