@JohnAb - thanks for pointing me in the right direction, 4001flashed successfully. It was in fact, Windows unzip that appears to be the culprit (I unzipped it with a freshly installed WinRar as you suggested). I had been using WinZip up until I went ...
I too skipped the 3901 Beta, on a 12900k/Z690 Hero here.
Keep getting "Incorrect BIOS" when trying to update. Downloaded the file twice from the Z690 Hero support page (and renamed the BIOIS before trying to update).
What about this: Do you use any third-party AV software?
If so, uninstall it for the duration of the upgrade. I'm on a Hero Z690 and I was getting stuck at a later stage than you (always 86%) until I uninstalled Norton 360 using their "Norton 360 Rem...
@Fringe09 - Corsair has just released ICUE v5.2.128 which is using an updated CPUID SDK. Finally, ICUE can display the NVIDIA 40-series Hotspot temperature.