VSS Snapshot warning. File c:\windows\servicing\version\10.0.149393.0\amd64_installed is not present on the snapshot.
VSS Snapshot warning. File c:\windows\servicing\version\10.0.149393.0\x86_installed is not present on the snapshot.
Figure 1

This issue is caused when Windows Server 2016 is updated by Windows Update. The below two files are removed by the Windows Update, but they are not properly un-registered from the VSS System Writer.
Windows Update changes the version of these two files:
C:\windows\servicing\version\10.0.14393.0\amd64_installed
C:\windows\servicing\version\10.0.14393.0\x86_installed
Microsoft has published the following Article on this issue:
Third-party backup warnings after you install a servicing update in Windows Server 2016
As per Microsoft, to fix the issue, create new placeholder files with the same name for the files that are reported as not found.
C:\windows\servicing\version\10.0.14393.0\amd64_installed
C:\windows\servicing\version\10.0.14393.0\x86_installed
NOTE: It may be necessary to assume ownership of the subfolders within the Version folder into which the files need to be created