We have virtual preschool meetings and invite "guest users" to participate in our Teams Channels and meetings. Every great now and again a Google Calendar user in the program who is an Attendee on the Teams meeting will delete one of the recurring dates to remove it from their Google Calendar. (For example if they are going on vacation and will not be attending.) The dates will get altered or removed for EVERYONE in the meeting (even the meeting organizer), and the organizer/attendees will all receive an email from email@example.com with the subject line "Updated invitation: ..." indicating the changes.
Normally invitees do not have the permission to alter Outlook or Teams meetings, just the meeting creator. I have worked with our IT department numerous times, and we have been unable to recreate the issue on our end and are at a loss on how to prevent it.