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Affects: Windows Server 2012R2, 2016, Windows 10
A new feature of UAC is to restrict access to administrive shares on non-domain systems. Thus, if you have an up-to-date Windows host in a Workgroup, you will be unable to back this system up using Q-Hybrid (the results are a WMI 'access is denied').
To get around this, one must disable the UAC restriction by making a charge in the registry on the affected Workgroup system:
This, followed by a reboot, will allow access to the admin$ and (drive)$ shares on the target system and will also allow Q-Hybrid jobs to function.
More information about the Administrative Share Restrictions can be found here