In regard to your concern, I would like to try the following steps:
-Make sure that you have the latest BIOS version. You can submit the model of your NUC at the following link, in order to get the BIOS downloads:
Drivers & Software (BIOS)
-Also, try to complete the manual installation of the latest graphic driver:
Uninstalling the Intel® Graphics Driver and Intel® Display HDMI/Audio Driver
How to Manually Install a Graphics Driver in Windows 7*
Intel® Graphics Driver [15.45] (Version: 184.108.40.20642 (Latest) Date: 11/9/2016)
-And make sure that you are not using any type of dongle or adapter, and use a straight connection.
Please let me know your findings.
I would like to know if the information provided to you was able to solve your concern?
In case if you need further assistance do not hesitate to reply back.
I am looking forward to hearing from you.
I followed up on your recommendation just today. I updated the BIOS (from 42) and the Graphics Driver (from version August, I think). I will monitor the situation this week and get back to you.
I forgot to mention the following:
I use two screens. 4K on DP and a 1280x1024 via HDMI.
This might be a totally different issue but I mention it just to be on the safe side.
When I drag a window with a size close to 4K from the 4K screen to the smaller one then I suddenly have a massive slowdown which lasts for a second or so. Then after it happened the slowdown cannot be experienced with that window anymore. If I return that window to the main screen, release dragging it, wait and then drag it again over to the other smaller monitor the slowdown can be observed again. As I said, possibly unrelated. It is not really a problem for me.
Please do not hesitate to let me know if the issue persists.
In regard to your latest concern, could you please provide me the brand and the model of the screens where you see this issue?
Hope I can hear from you soon.