Hello,
We have been having an issue for the last week with our Windows Server Backup failing on our Windows Server 2016 Essentials server. It is failing with the application event ID 517. The backup operation has failed with the following error code '0x807800AF' (The Volume Shadow Copy Service backup complete operation failed. The backup backs up the EFI System partition, local disk with all the data, Bare metal recovery, but fails on the System state. It says the Backup canceled. System state backup was canceled.
The error in the windows server backup software is the Volume Shadow Copy Service backup complete operation failed. A volume shadow copy service component encountered an unexpected error.
The server has been rebooted and we will get one working backup but the issue returns the following day.