Error Message When Saving Schedule using iCal (Mac Calendar)

I keep getting an error message (screen shot attached) in the Mac Calendar after saving the schedule to iCal. It seems to pop up each time when I either first saved the schedule or try to make a change to any part of the calendar.

This issue may only or more related to the iCloud Calendar. That is, the error message seems to pop up only when I saved to the iCloud Calendars and none when saved to the "RIT" Calendar.

RIT Calendar - RIT google account calendar that's synced to the Mac Calendar.