I recently updated my Haswell i7 Brix (GB-BXi7-4500) to Win10. After the upgrade, I downloaded the production Win10 driver (version 220.127.116.11.4256). and after installation, I feel thrown back to the past.
I have a Dell UP3214Q display - one of those infamous dual tile displays where you only get 4K at 60Hz if you operate the display in MST mode. For the longest time, this posed a problem for intel's drivers - but recently it got better and better and recent drivers for Windows 8.1 even managed to restore the picture size and position after a display power cycle).
Well, on Win10.. the old problems are back. If I switch between the two inputs, I don't get a picture anymore (was no problem prior to the update.. and my HP Elitebook 840 G1 operating on driver 18.104.22.168.4251 has no such issues) and I need to power cycle the screen. it then comes back with every window moved to the upper lerft corner at minimal resolution (I believe it's 1024x786).
So, I think somebody should have a look at what's different between the W8 and W10 drivers when connected to such a screen. Mine is a REVA02 by the way so it contains the fixes for the infamous "no picture" issue.
I have the very same issue on my intel NUC5i5RYH. Neither of the affected device has any issues on Windows 8 - thus the problem must be the drivers.
You can try updating the Intel® NUC Kit NUC5i5RYH Graphics to version 4256, driver release date 08/05/2015. https://downloadcenter.intel.com/download/25150/Intel-Iris-Iris-Pro-and-HD-Graphics-Production-Driver-for-Windows-10-64-bit