Outlook Meeting invite changes sending cancelation instead of update

Hello, 

I am having an issue with Outlook Meeting Invite updates within my organization and need some help. It has been brought to my attention that for the last few months staff have been noticing an issue when they send a meeting invite out (either from Outlook on the Web or Outlook for Mac) everything works correctly. However if they update the invite (add an agenda in the description area, or attach a document, or add another individual to the attendee section) and click send update, all of the attendees will receive a Meeting Cancelation Notice and then a few minutes later will receive a new meeting invite with changes that were made. 

Is there a setting am missing in exchange that is causing this? I have watched a number of staff go through the steps and it looks correct. They click on the meeting, then edit, the meeting dialogue window opens and they add the agenda or the additional attendee and then click send update. 

Any help or direction would be greatly appreciated!