KB 2918371 describes the following issue with Windows Server Backup 2012:
- Environment: a Windows Server 2012 Hyper-V host and a Windows Server 2012 guest virtual machine (VM).
- Open Windows Server Backup on the host operating system.
- Select Backup Schedule to start the backup schedule wizard and then click Next.
- Click Custom on the Select Backup Configuration tab and then click Next.
- Select Add Items, select the host component and the guest VM, and then complete the wizard.
- Restart the host operating system.
You could try to fix the issue by downloading the hotfix at:
To our knowledge, the above bug affects only Microsoft’s own software.
Alternatively, download BackupChain Hyper-V Backup and back up your virtual machines using BackupChain.
It installs on Windows Server 2008, 2012 / R2, as well as Windows 8 and offers dozens of additional backup features, such as incremental / differential deduplication, granular backups, granular restores, NAS and USB backups, and much more.