Meeting Forward - unrelated to sender

Are there any known issues related to meeting forwards in Exchange Online?  

I have a few users who are reporting that meetings were forwarded from their email address that they didn't send.  The people experiencing the issue were not attendees of the meeting or even related to the people in the meeting.

One of the users had the mobile shared calendars show up earlier in the week also, wondering if its related.  That user also used the native iOS mail app.