Some things to try;
- sfc /scannow
- dism /online /cleanup-image /restorehealth
- https://support.microsoft.com/en-au/help/4027322/windows-update-troubleshooter
- or possibly removing the most recent successful cumulative update. and try installing latest update again.
- repair install by running setup.exe from the root of install media
- or also by pouring over the \dism.log, \windowsupdate.log, \cbs.log looking for and replacing the missing files from another server,
More than likely the quicker thing to do is standup a new one, patch it fully, migrate roles over and move on.
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