When trying to move a Notification Record to a different environment via update set, the event name is not showing correctly and defaulting to the first selection in the dropdown list. The preview of the update set also does not catch this non-existing event name.
Since the "event name" is a string field and not a reference field, the update set preview will not detect an error. If the event name registry record does not get moved over in the update set, the event name field will automatically default to the first selection in the dropdown list. If you check the XML for the notification record, you will see the correct event name, but the dropdown selections for that field on the notification record will not exist.
When moving notification records via through update set, be sure to also move the event registry record in the update set as well.