I just did two fresh installs of Win 11 Pro and I learnt something related to WHEA errors on my 690 Hero.

For the first install, I did not install Armoury Crate (turned off the install option in BIOS) and added all of the drivers manually from the motherboard support page. After a few hours I noticed (in HWInfo) that I was getting around 30 WHEA errors per minute. Unlike your errors, these were not fatal and had ID=17. Disk transfers were slower than normal and would eventually virtually stop. Reboots were also taking a long time and the errors were related to the PCIe bus. I did some digging, but couldn't track them down to a specific device in Event Viewer.

I had never had such errors before, so I decided to reinstall again and I used Armoury Crate to install all of the drivers. The only driver I added manually was the 'Rapid Storage Technology Driver' which can be downloaded from Armoury Crate in the tools/individual kits section. This is needed to setup RAID drivers, even though I don't use them and get rid of the yellow warning symbol for the PC in 'Devices and Printers'. Everything is now working perfectly. Not a single WHEA error after 18 hours.

Bit of a long shot, but might be worth a try? I assume you have set BIOS to defaults as well with XMP off for now? Also, have you changed your BIOS recently?