Update the BIOS
Download the BIOS latest version at:
https://downloadcenter.intel.com/product/85254/Intel-NUC-Kit-NUC5CPYH
The file must be the "Express BIOS update".
Unarchive and put the ".bio" file at the root of a usb key.
Insert the key in the server.
Then click on F7 while booting in order to access the "BIOS Flash Update tool".
Go to the "Boot" menu and activate "USB Boot".
Pick the usb key, then the ".bio" file and follow the process.
Remove the key once it is done and reboot.