Meeting fwd notifications and cancellations

1) A meeting invite is on a generic mailbox calendar. Outlook forwarded it
to all the people on the invite from User A's mailbox on behalf of the group
calendar. User A confirmed that she didn’t send it. Our issue is that it
does not sync up with the generic mailbox calendar invite, so it showed up
twice in people’s calendars. And, if I update the invite on the group
calendar, it will not update the second invite that was sent from User A's
mailbox.
2) Another thing that is happening is that cancellations for this meeting
invite will go to everyone on the list when either someone deletes it from
their calendar, or Outlook does it by itself (even though it will say someone
did it).

Help!! We have been seeing this on other mailboxes as well.