Items such as Draft emails and Calendar items, that are not replaced with an Enterprise Vault Archived Item Shortcut by default, may be re-archived multiple times if these items are of a large size. In testing, emails in the Drafts folder that were larger than approximately 100MB were affected by this problem.
The large size of the item affects the time taken to complete its archival and post-processing. As a result, the Archived Date of the item is recorded as being prior to the Last Modification Time. The next time the Archive Task runs, this is interpreted as meaning that the item has been modified since it was archived, and therefore it needs to be re-archived. As the size of the item has not changed, the same set of events will occur again and again.
This issue has been addressed in the following release:
Symantec Enterprise Vault 11.0 0 Release Details