I am up to 2 computer with Win10 Pro AU (1607). One is a Toshiba Satellite S50C, the other a Dell XPS 980. Both are set for Fast Startup which means they also do hybrid shut downs where the kernel is saved rather than shut down, too, IIRC.

With both, I use the Start Button context (right-click) menu "Shut down or sign off>Shut down" to shut the computers down. When I install, in my case, new NVIDIA driver software Monday and Win10 Updates yesterday (Tuesday), and after the restarts to install the drivers and the updates, when I go to shut the computers down, the computers just sit for about 5 minutes before actually starting to shut down.

To be clear, the computer just sits there staring back at me. The shut down screen does not come up for about 5 minutes, but when it does the shut down proceeds with its typical speed. After that, shut downs will begin promptly after clicking "Shut down".

I can only speculate, but I wonder if the computer has to do something in the background because of the new installation of software and system updates before it will let the shut down process proceed.

I'm posting this because I want to see if anyone else has seen this behavior especially since I am seeing this fairly consistently on 2 computers now after the above mentioned installations.