Just started using eM client for G-sync and the sync added 3 instances of same meeting in the calender.
Try the repair feature on the calendar after you right-click on the calendar and choose Properties > Repair.
Russel, now i have 6 instances
In this case, it seems as a corrupted calendar file. If it is the only appearance of this issue, just try removing the event and create it again from eM Client.