TL;DR: New CPU fixed the issue.
As the original poster, I’ve resolved my issue, but I’m not marking it as “fixed” since many people are facing similar issues, and my solution wasn’t straightforward (or cheap).
After extensive troubleshooting with Windows, BIOS updates and rollbacks, platform and GPU drivers, numerous settings adjustments, and multiple reinstalls and repairs of Diablo 4, I decided to swap out my DDR5 RAM for a different set, hoping this would solve the issue.
No change. I then tried a new motherboard, using both my original RAM and a spare set I had (even purchased a new set). Still no change.
Being a PC enthusiast, I have a closet full of parts, so I kept testing.
I eventually tried a third motherboard from a different manufacturer (ASRock Taichi, MSI Tomahawk, and Asus Strix, all on the Z790 chipset). But yet again, no improvement.
After further testing, it turned out that my 13900K had a degraded memory controller. I managed to keep the system somewhat stable by switching to single-channel mode instead of dual, but it wasn’t a real solution—Diablo 4 still crashed.
Finally, after monitoring temperatures and noticing unusual fluctuations in power demand, I replaced my 13900K with a 14900KF, and the issues disappeared immediately.
I know it might sound petty, but I still suspect Diablo 4 contributed to this. I never had issues before the 2.0 update, and since then, I’ve seen (as we all have) Diablo 4 consume massive amounts of RAM and heavily utilize the page file.
My 13900K is a couple of years old, so it could be normal wear and tear, but I believe the latest D4 build put excessive stress on both RAM and the memory controller. This situation is rare, but not unheard of. I wasn’t running any overclocks other than XMP, and I even disabled XMP during most of my troubleshooting.
As a water-cooling hobbyist, temperatures were always under control and never close to TJmax, but I did notice odd and intermittent temperature spikes during my testing, which only increased my suspicion.
Since installing the new CPU, my system now handles 64GB of RAM in dual-channel setup perfectly, and I’ve played D4 for hours without any issues or crashing. I haven’t even needed to adjust the page file with the new hardware.
If you’re facing similar issues, I recommend monitoring CPU temps and power usage, particularly around the memory controller (VCCSA and VDDQ). Also, pay close attention to power draw of these, the VCORE, and your GPU compared to your PSU’s output. Inconsistent or (dirty) power could also lead to issues like mine.
This may not be the exact issue others are experiencing, but it’s worth investigating if you have the option.