You may see the message 'The VSS system writer is missing' when trying to do backups on your server. This issue is due to the disappearance of the VSS System writer.
As a result of one of the requirements with MES, ASP .NET temporary files get created, which results in the System Writer being unavailable. The only solution is to delete the following folders to restore VSS Full System backups:
C:\Windows\Microsoft.NET\Framework\v2.0.50727\Temporary ASP.NET Files\
C:\Windows\Microsoft.NET\Framework\v4.0.30319\Temporary ASP.NET Files\
C:\Windows\Microsoft.NET\Framework64\v2.0.50727\Temporary ASP.NET Files\
C:\Windows\Microsoft.NET\Framework64\v4.0.30319\Temporary ASP.NET Files\
This is a known flaw for which a fix was made for Windows Server 2008 but not 2012 R2 or 2016. Some more information can be found from these technet articles: