Under certain circumstances Storage Expiry may not expire eligible items. If millions of items are on Legal Hold, the expiry process includes those items while checking for eligible items. This can take many hours depending on the amount of items on Legal Hold. As a result, items that are not on Legal Hold and are eligible for expiry may not be processed.
This issue has been addressed as part of the following release:
Enterprise Vault 9.0.4 - Release Details
Enterprise Vault 10.0.1 - Release Details