Policy is not being applied to a mailbox and Event ID 8 for Exchange Store Manager is seen in the Event logs. Also, the error below is seen in the corresponding wlog for the mailbox:
 Unspecified error
Error: The client operation failed.
Component: Microsoft Exchange Server Information Store
Low level error: 000004DD
This can be caused by an Exchange quota limit being exceeded for the mailbox in question.
Remove or relax the quota limit for the mailbox in question until the Exchange Store Manager service completes its crawl of the mailbox. You could also move items out of the mailbox into a PST file.