I have 3 machines from a lot of 24 which are experiencing some odd issues. When I shutdown the machine, whether it is from Run, CMD, Alt-F4, or start menu, the system will not do anything for a good minute. It almost appears that the button does not function at all. I should also mention that pressing the physical power button on the case does not prompt a shutdown either, despite the power options being set to do so. I can still open all programs on the machine after clicking shutdown and they will open, with the exception of Optimise Drives which takes 30 seconds - 1 minute to open, which is another odd behaviour all 3 are exhibiting. After a minute passes, the machines will start shutting down, but they will take a long time to do so, with little to no drive activity. Once the display eventually turns off, the machines will run for a while longer, again with no drive activity, before eventually powering off. I've read that this black screen issue is common among the 1803 update, but nothing about Windows refusing to shutdown. On some occasions, I have had a couple of the 3 flaky machines post (CPU Fan ramps up and down which usually immediately precedes Windows loading), but the display will not receive a signal for roughly a minute. Once the video shows, the Gigabyte BIOS logo will hang for 1-2 minutes and eventually to proceed to boot Windows normally. All of the machines have an identical image of Windows 10, as it was cloned from the same drive for each machine. All BIOS revisions are the same, and all systems are as up to date as possible as of 16/07/2018. I have tried reinstalling all drivers, swapping PSU's and SSD's with known good parts, removed GPU's and used IGPU's with no luck. I tried different SATA ports and versions (3.0 & 2.0). I have also tried disabling fast startup in Windows because I read that this is another common cause. The specs of the machines are:
Intel Core i5 4460
Antec VSK3000B Black Micro ATX Case with stock 500W PSU
8GB of generic DDR3 1600MHz Ram (2x4GB sticks)
Kingston SSDNow V300 120GB SSD
Gigabyte GTX 750 2GB
Generic USB 2.0 Internal Card Reader
I am lost as to why only 3 of the 24 machines are experiencing these issues. Each computer has been stress tested using Asus RealBench and the drive health checked by Crystal Disk Info. Any advice as to why these machines would be acting up is much appreciated!