Fix applies to Windows 8.1, Windows RT 8.1, Windows Server 2012 R2, Windows 8, Windows RT, Windows Server 2012, Windows 7 Service Pack 1 (SP1), or Windows Server 2008 R2 SP1 OS's only
In this scenario, the backup task fails, and you may receive the following error message that states the Volume Shadow Copy Service (VSS) failed because of a time-out:
FAILED_AT_FREEZE (0x800423f2 - VSS_E_WRITERERROR_TIMEOUT)
The issue occurs because the VSS encounters a deadlock during the Thaw event if the Security Account Manager (SAM) has pending writes for the registry.
Microsoft has documented this error and provided a fix, note that this fix has a pre-requisite: