We've ben tracking an issue where the name of the object in the alert does not match the current name of an object.
(pedantically we use the IP address for our edge switches, when they renumber the name changes)
the AlertObject table doesn't track changes in caption, and it's the value initially stored in that table that gets displayed in the ActiveAlerts / AllAlerts widget.
Try this database query in your environment to find nodes where the alert captions will not match the [current] node name.
FROM [dbo].[AlertObjects] AO inner join nodes N on
where AO.EntityCaption<>N.Caption or AO.RelatedNodeCaption<>N.Caption
Bug report being filed with SW Support