Computer restarts when starting demanding game after BIOS update

I have been experiencing computer restarts when some high demanding game loads. This happened after i updated my Asus TUF B760M-PLUS D4's BIOS from 1820 to 1836.

I have attempted to flashback to previous bios but it made it worst, where it restarts when i attempt to sign in to my Windows. So I update back to the latest one again where its stable as long i dont play any games.

After some troubleshootings, i suspect its the PSU after OCCT's power test. It just failed in the first 2 secs.

Does anyone has any idea what caused this? Ill try to put down my specs and troubleshooting below.

Spec:

MB: Asus TUF B760M-PLUS D4

CPU: Intel I5-14600kf

Mem: Corsair Vengeance RGB Pro 32gb DDR4 3200mhz

GPU: Gigabyte 4070 Gaming OC

PSU: Corsair RM850 (should be the 2023 model, build this pc around early-mid 2023)

Troubleshooting attempts (all failed)

1. BIOS flashback

2. CMOS reset

3. Reupdate bios

4. Ran without xmp & default bios settings

5. Connected gpu to the lower PCIE

6. Swapped around the PSU modular slot for the CPU and PCIE cable

7. RAM reseat

8. Reformat

9. Swapped with different GPU

10. Ran Intel Diagnostic Tool, so far passed

11. Havent run Cinebench or other stress test, so far CPU test running fine on OCCT.

12. Downvolted CPU power draw. No adjustment on GPU end.