Just a note about the upgrade process:
On my Corsair ONE the screen remained blank after it booted from the USB stick the first time. I assumed it flashed the BIOS during this time as it asked my Bitlocker password when it rebooted automatically after a minute or two.
I ran the M-FLASH process afterwards and everything seems to be fine.
Is this a scenario that you came across? Could it be because my Corsair ONE is connected to a 4K monitor through a DisplayPort? Did the first flash actually go through, is there a way to check that?
My system information says it's running 4C3.