VSS errors related to NTDS writer failures - Veeam Software
https://www.veeam.com/kb169703.12.2012 · As these errors are related to the Microsoft VSS subsystem, a reboot often is the fastest way to alleviate any issue which may be occurring at the OS level. Disabling the anti-virus temporarily can help isolate whether the issue is related to interference from the anti-virus. Disable\uninstall the anti-virus fully and run the Veeam job.