Calendar edits make events show on old accounts

We have a girl who joined in 2018, but when you look at her participation record, it shows events from 2017, before she even joined. Of course they are marked “did not attend”, however, why are they even on there in the first place?

I’ve been told that if any point, someone goes back to a previous calendar event and does any kind of editing, it will pick up all the current members and add their names to it, even if they were not even members of the troop yet.

Any way to clean this up?