Hi,
If a client is able to download update from WSUS server, the WSUS should be fine. It may be an update specific issue. Please try to download the update manually from the website below:
http://catalog.update.microsoft.com/v7/site/Home.aspx
If the manual installation is still failed, please try to use DISM or System Update Readiness tool to check if there is any system file corruption.
https://support.microsoft.com/en-us/kb/947821
Best Regards.
Steven Lee Please remember to mark the replies as answers if they help and unmark them if they provide no help. If you have feedback for TechNet Support, contact tnmff@microsoft.com.