New PC build: Ryzen 9 9950X3D + 64GB DDR5 stuck on POST code 08

[HELP] New PC build: Ryzen 9 9950X3D + 64GB DDR5 stuck on POST code 08 after reboot or BIOS changes

Specs: • CPU: AMD Ryzen 9 9950X3D • Motherboard: Gigabyte X870 AORUS ULTRA WIFI7 • RAM: 64GB DDR5 (2×32GB Kingston Fury Beast 6000 CL30, KF560C30BBEK2-64) • GPU: Gigabyte RTX 5090 OC • BIOS: Latest version (flashed using Q-Flash Plus)

Issue: After a CMOS reset, the system boots — I can enter the BIOS or install Windows. But: • As soon as I complete Windows setup and the system reboots, it hangs on POST code 08 • The same happens if I make any BIOS change — it fails at 08 during memory training • Only a new CMOS reset gets it to boot again

What I’ve tried: • Flashed BIOS via Q-Flash Plus • Booted with only 1 stick in slot A2, then added the second in B2 • Manually set: • Memory multiplier to DDR5-3600 or 4000 • DDR_VDD / VDDQ to 1.25V • tCL / tRCD / tRP = 40, tRAS = 80 • Memory Context Restore = Enabled, Power Down = Disabled

Still, it consistently fails on reboot unless I fully reset CMOS again.

Any ideas? Could this be my RAM kit being too aggressive, or is it a BIOS-level bug on this board?