Mine is nuc8i7hvk. At present Intel's official website does not have a method to downgrade for nuc8i7hvk. Other models could download a bios recovery file, but nuc8i7hvk does not provide recovery files.
You can downgrade your Bios to version 0058, use the following method:
Prepare USB stick fully formatted to FAT32 (disable quick format option during format). Format your USB on Windows machine (rather than Linux or MAC). Save the Bios file HN0058.bio (https://downloadcenter.intel.com/download/28953/BIOS-Update-HNKBLi70-86A-) on this stick and insert it into front USB slot with amber color (NUC shall be OFF). You may use also one of the rear USB ports (do not use front blue USB port, since sometime the USB stick is not recognized during boot process).
Press Power Button for about 3 seconds. Count 1001, 1002, 1003,1004. Release the Power Button. NUC should reboot into Power Button Menu. You should release the Power Button before 4-sec shut down override or when the Power Button LED changes color from blue to amber.
Press F4 and the recovery shall start (it can take up to 30 seconds for messages to appear on the screen).
When the recovery finishes, press on Power Button and hold it, until NUC switches OFF. Pull out the power cord. Remove the USB stick.
Replace the power cord and press Power Button to switch the computer to ON.
Enter Bios setting by pressing F2 during boot process.
Press F9(followed by "Y"), to set Bios to default settings. Press F10 (followed by "Y"), to save the settings and exit to O.S. Let the NUC fully reboot.
If before update, you have customized bios settings, you can enter again to Bios setting to change the necessary settings.
