Why do I have duplicate calendar items with migration from G Suite?
Duplicate calendar items can be created when the Source is G Suite, and the resource or location of calendar items is changed while a migration is occurring.
This is because when the location of an event is updated, Google will create another item with another ID. The updated item will have a new ID, where, for example, "_R2014……” is appended to the original one. This is the item which will then be migrated - as a duplicate.