We have this issue on our Windows Backup issue (wbadmin) from one of our Hyper-V server. We haven't got any backup issues till we applied one of the Windows updates.
Windows Server 2012 R2
The Hyper-V and VM backups is pointing to USB portable device.
USB portable device is apart of Disk 2 Basic appearing in Disk Management (Disk 0: primary physical disk partition, Disk 1: Mini disk storage - 18GB)
Microsoft Hyper-V VSS Writer The writer experienced a partial failure. Check the component level error state for more information. (0x80042336) Unspecified error (0x80004005)
What we did so far:
Rebooting the machines few time >>> No luck
Apply the Autoamount command on DISKPART >>> No luck
We managed to solve this issue. After looking intensively on the Event Logs under Applications and Service Logs / Microsoft / Windows / Hyper-V-XXXXXX and we found the permission issue - General access denied error (0x80070005). It's missing the "NT VIRTUAL MACHINE[VM-GUID]" on our Virtual Machines directory.
Apply this ICacls and it worked nicely - the backup is working ok now.
D:\Virtual Machines>icacls "D:\Virtual Machines\xxAUxxxSQD01-VM" /T /grant "NT VIRTUAL MACHINE\C2C11601-0A27-4E61-AF82-34D3C866AFDA":(F)
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