WIth Exchange Server 2013 CU11 and Exchange 2016 CU1 the Exchange Product Group introduced a new feature named Mailbox Anchoring.
The workaround provided by Veritas in KB article 107463 recommends to set a new registry key for the NetBackup process responsible for running PowerShell queries.
There is no guarantee that this workaround will fix your backup issuesd with Exchange Server 2013 CU11 or Exchange Server 2016 CU1. It seems that the only workaround is by creating a new service account for NetBackup service due to rights assignments being removed during Exchange Server CU setup.
Enjoy classic backup with Exchange Server 2013 and Exchange Server 2016.