#FRESH DOWNLOAD COULD NOT TAKE OVER THE DOWNLOAD INSTALL#
The dumb thing about CU is that it may need most of the updates to be in.then some updates need older updates to be in.but Windows updates do not go by that sequence (I do not really know what sequence they use) so I notice that sometimes Windows installs update A halfway then stops to see if update B have been installed.then reverts update A to install update B then installs update A.thats where it takes a long time. I would always reboot the server and clear up some locations before Windows updating.Windows Temp folder, c:\windows\software distribution folder (needs to stop Windows update service first), set pagefile min=max=recommended (one time only). When I notice that there are a lot of updates.I would plan a "servers update window" to update all or most of the servers. I would set the server to "download but not install". I would usually use one of the servers as a template (its one of my DCs as it is usually most updates). My 2008 & 2012 servers are done in about 15-30 minutes depending on how many updates there are and I can do them all simultaneously.
I've never had so much trouble till moving to Server 2016 and have used WSUS for years. I will try the manual update you suggested for next month and see how it goes. I looked over the biggest offender's event log and no smoking gun identified. Once server A hits the reboot stage, then I start server B and so forth.
If server A takes 3 hours to "prepare to install updates" then it takes about 2 hours to go through the reboot process, which includes the whole "installing" series of screens.