The event created on the calendar via exchangelib/EWS is duplicated

Question

My project uses exchangelib to create events on my calendar.

from exchangelib.items import CalendarItem

calendar_item = CalendarItem(folder=kwargs['folder'], subject=kwargs['subject'],
                                     start=start,
                                     end=end, body=kwargs['body'],
                                     _end_timezone=TZ, _start_timezone=TZ,
                                     **optional_data)
calendar_item.save()

Sometimes, my event is created twice (duplicate).
Has anyone ever had this problem ?
Could this problem come from EWS or exchangelib ?