Viewing Calenadr Event sends an update to all invitees
This appears to be a new bug in iOS9.
If you go into calendar and VIEW an event and then go back, it will send an update to all attendees even though you didn't change anything.
For example, if I have a meeting at noon and open the event 30 mins prior to copy or map the address, when I go back out of the event, it sends an update to all attendees.