KB1735: The specified network name is no longer available
https://www.veeam.com/kb173522.02.2013 · For example, if connections from any Windows server on an ESXi host tend to fail, but connections from a physical Windows machine do not fail, the root cause probably involves that ESXi host or its network connection. If the SMB connection consistently fails after 10 hours, it may be due to expiration of a Kerberos service ticket.