When deleting an element using PI System Explorer, there should be an option to delete all event frames that reference the element. Currently when deleting an element, the delete option "Delete this object and all references to it" does not delete the event frames that reference the element. This delete option only deletes the references that are inside the event frames.
If a deletion of an element occurs, then there could be lots of undesired event frames that have no referenced element in the database. And to find these event frames, it would be necessary to use another tool such as PI Builder to somehow filter the event frames in the AF database to the specific ones that just lost their referenced element.