I replaced my MSI X870E Carbon WiFi and MSI RTX 5090 Suprim with an ASUS ROG Crosshair X870E Dark Hero and ASUS RTX 5090 Astral. The Ryzen 7 9800X3D, RAM, PSU, and storage stayed the same. Since the hardware change, some games have random framerate spikes and overall performance feels less stable, including noticeably more VRR flicker.
I performed a fresh Windows installation and kept the software setup largely the same. I have also reinstalled the GPU drivers, updated the chipset drivers and BIOS, tested with EXPO enabled and disabled, reset the BIOS, and reinstalled Windows a second time. None of these steps fixed the issue. The problems remain even when running without the RAM profile, and I am not using any manual overclock.
2 Answers
Have you tested the system completely at stock settings? The standard RAM profile counts as an overclock on many platforms, so it would be worth disabling EXPO and leaving every CPU, memory, and GPU setting at default while testing. Since the issue still happens without EXPO, that makes it less likely to be the sole cause, but it helps eliminate memory tuning as a variable.
Because the graphics card was replaced as part of an RMA, it may be useful to treat the new GPU as a separate variable rather than assuming the motherboard is responsible. Compare the behavior across several games and, if possible, test with another graphics card or in another system. That can help determine whether the problem follows the new card or remains with the rest of the build.

Yes, I tested with EXPO disabled and no manual overclocking, but the stutters and VRR flicker still occur.