Is that using shut down button within windows? Or using reset button on your case?

When you tried the new BIOS did you tweak your settings to get stable, before saying it doesn't work? You can't always use the exact same old BIOS settings between versions, so you need to test for stability before you decide.

And of course be sure you start by loading optimized after the flash, then save/apply/reboot back to BIOS to make all changes you need to make. Clearing the DMI pool while flashing is also suggested.

Great to hear F4 works for you though, at least you do have a BIOS you can use so that's a plus