New-MailboxExportRequest gives PSTs which need repairing

Hi,

We're currently exporting a large number of mailboxes to PST in preparation for an Office 365 migration using the New-MailboxExportRequest command as follows: New-MailboxExportRequest -Mailbox $username -ContentFilter {Received -lt $date } -BadItemLimit 50 -FilePath \\servername\archives -MRSServer CAS1

This works however the archives contain a large number of corrupt items (in the hundreds) and need to be repaired using PST repair tool.

How can we prevent this from happening?

Thanks,
Bryan