The first thing to try if Windows Updates fail is:

sfc /scannow

If it doesn't complete, try something like:

chkdsk /x /f /r
y
shutdown now -t 0

then:

dism /online /cleanup-image /restorehealth
sfc /scannow
shutdown now -t 0

https://serverfault.com/questions/625332/windows-update-not-working-on-windows-2012-r2-standard

1. Stop the Windows Update service:
   1. net stop wuauserv
2. Delete the Windows Update cache directory C:\Windows\SoftwareDistribution
   1. Remove-Item -Recurse -Force C:\Windows\SoftwareDistribution
3. Restart the computer
   1. It may require several restarts to get everything deleted from this directory
4. Run Windows Update manually again
   1. It will fail almost instantly and offer to run a diagnostic tool
   2. Download the tool and allow it to run
   3. http://go.microsoft.com/?linkid=9830262
5. The tool will find and fix some problems
   1. Reboot the server
   2. Wait a while, or you may get another error
   3. Run Windows Update manually again

Take these steps to reliably fix troublesome Windows Updates:

1. Turn off automatic updating
   • Control Panel → Windows Updates → Change Settings → Never Check…
2. Reboot
3. Search the Internet for “Windows XX latest update client”
   • Where XX is your Windows version
4. Download and install the latest update client for your version of Windows
5. Install Windows Updates