My specs:
-MAXIMUS VIII Impact (running latest BIOS 3401)
-i5 6600K (OC'd to 4.4 at 1.35v)
-16GB DDR4 RAM (XMP profile)
-Intel 750 U.2 drive (running latest firmware 8EV101H0)
-Windows 10 64-bit (running latest version 1703, 15063.483)
-UEFI completely (CMS disabled, Secure Boot disabled, Fast Boot disabled)
-Installed Windows 10 64-bit via USB (formatted using Rufus) - partition scheme of GPT for UEFI (no MBR) and FAT32
-no SATA drives or external drives installed/attached
-OC is pretty basic/nothing fancy
-Windows 10 has "Turn on fast startup" disabled/unchecked
I've had this same setup for a while now, and it's never given me any trouble. However, ever since upgrading the BIOS to 3401, I run into this odd issue where it will automatically boot into BIOS (BIOS shows the Windows Boot partition as first and only boot in the boot order, so it know it's there). Hitting F10 to restart will automatically boot into Windows like normal. Annoying and curious, but it works.
Out of every 1 of maybe 10 times, WIndows will randomly fail to boot up at all. It will act like it's booting into Windows, then show the "Repairing startup", and say it can't automatically fix it. No amount of reboots/repairs/etc. will allow the BIOS to recognize that the Windows Boot partition is there (again, BIOS still shows the Windows Boot partition as first and only boot in the boot order). To easily bypass this, I boot into my same Windows install USB, click "Repair this computer", and then select the Boot into Windows as Normal option. The computer restarts, and Windows 10 boots up like normal. Then the whole ordeal starts over (cold booting brings me to the BIOS, restarting boots into Windows, then roughly 10 or so times later of cold boots it fails to boot into Windows entirely).
I've tried different reformatted several times, ISO images, different USB sticks, etc. - the above issues still persist. I never had this issue before with the previous BIOS firmware (can't recall which version it was). Please help!