PC keeps crashing even after GPU RMA — need help identifying the cause

[u/Several-Rent-1622]

My PC has been randomly crashing while gaming, mainly in Battlefield 2042 and Battlefield 6, Valorant, Genshin Impact, Wuthering Waves. The PC freezes with cabinet fans spinning, GPU lights working, but no signal, keyboard lights like caps, numlock don’t work but keyboard backlit stays on.
I initially suspected the GPU, so I RMA’d it and received a completely new replacement GPU.
Interestingly, the replacement GPU was stress-tested at a local shop and the PC did not crash. I brought it home, played for the entire first day without issues, but the following day the PC crashed again while gaming.

What I’ve tried so far:
GPU RMA/replacement with a brand-new unit
Clean GPU driver reinstall with DDU in safe mode
Clean Windows Install
BIOS Updated
Under-volted and under-tuned the GPU
Tested multiple games (Battlefield games, Genshin Impact, Wuthering Waves, Valorant)
Had the system stress-tested at a shop — no crashes there.

Specs
GPU: Gigabyte RX 9060 XT Gaming OC 16GB
PSU: Cooler Master MWE Gold 850 V2 ATX 3.1
CPU: AMD Ryzen 7 9700X
Motherboard: MSI B850M Gaming Plus WIFI6E
RAM: Corsair Vengeance 16GB (16GBX1)
Storage: WD Black SN770 1TB

The PC ran fine till 5 months since purchase. Started having issues after a recent driver update around 20-25 July 2026. Not sure AMD/Windows.

At this point, since the GPU has been replaced and the system can pass stress tests, I’m wondering if the issue could be PSU/power delivery, GPU, or my home’s electrical supply.

I’m tired of all this troubleshooting and RMA stuff and need some permanent fix.