What does the Microsoft Calendar Repair Assistant (CRA) do?
Calendar Repair Assistant (CRA) runs and reviews the chair and invitee's calendar, if there is no matching meeting between the two calendars, CRA will replace the meeting, thinking the deletion (missing meeting) was done in error and requires repair.
Calendar items should never be deleted from the target mailbox. CRA thinks a Delete is a mistake on the user’s part, and will replace the calendar item.
Meetings must be Accepted or Declined, never deleted. If a user is invited to a meeting, and deletes it rather than Decline the invite, CRA will add the meeting back to the user's calendar.