Calendar appointments disappearing after I close the reminder pop up
Events that are on my calendar will pop up as a reminder right before the event. I generally click "Close" because there is still some time until the appointment. Then when it's time for the appointment, I go to my calendar to find the phone number I need to call into, and the appointment has been deleted from my phone. It only seems to be happening to appointments that someone else created and invited me to. I can still see my own appointments I created.
Note: I am only using calendar items that were created/accepted via Outlook, but am trying to access the info from my synced iphone 6.
iPhone 6, iOS 8.4