Question Black screen, GPU fans spinning full speed and top fans (SYS_FAN3) stop spinning after startup or wake up

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Specs:
GPU: ASUS DUAL RTX 2060 OC EVO 6 GB (DUAL-RTX2060-O6G-EVO)
CPU: AMD Ryzen 5 5600X
PSU: be quiet! Pure Power 12 850W
RAM: G.Skill Ripjaws V (Black) (4x8 GB) 32 GB 3200 MHz
Motherboard: Gigabyte AORUS B450 Elite V2
SSD: SiliconPower A80 256 GB NVMe
SSD: Kingston NV2 2 TB NVMe (SNV2S/2000G)
SSD: Samsung 860 EVO 500 GB SATA 2.5''
Description:
I've had this for about 2 years now. This happens only immediately after startup or wake up from sleep, only if I don't move the mouse or start using PC right away. For example, PC wakes up from sleep (I wake it up with mouse - click or just move or with keyboard) and then leave it on lock screen, so no further use, and after 10-20 sec. this issue happens (black screen, GPU fans spinning, top fans stop spinning connected on SYS_FAN3). It's the same on startup, PC normally boots to Windows and then leave it on desktop, no further use, after a few seconds this issue happens. This doesn't happen everytime, it happens about 75% of the time. When this happens, the only way to shut down PC is to turn off a switch on PSU or remove power cable, I can't turn it off by holding a power button. And if I start using PC immediatley after startup or wake up, everything works normally, without any problems. During the first year of this problem, I also noticed that the BIOS was reset after the shutdown, and now for the last year, BIOS is not resetting anymore. Hope you understand my situation.
What I've tried:
Changing GPU with new one - from Gainward RTX 2060 Ghost to ASUS DUAL RTX 2060
Changing PSU with new one - from be quiet! Straight Power 11 750W (died half a year ago) to Pure Power 12 850W
Re-seating RAM
Re-seating the GPU and its power cable
Re-seating and checking CMOS battery
BIOS is up-to-date and on factory defaults
Turning off XMP
GPU drivers are up-to-date
Reinstalling GPU driver
Reinstalling Windows 11
Windows and all drivers are up-to-date
Automatic restart is disabled

Unfortunately none of the above fixed. I suspect that the problem is in the motherboard.
Does anyone have a solution for this? Is there some kind of trick to fix this or some setting in Windows or BIOS, before I replace the motherboard?

 

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Motherboard: Gigabyte AORUS B450 Elite V2
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BIOS is up-to-date and on factory defaults
What BIOS version are you on for your motherboard? If you've flashed the BIOS to the latest(which you should clarify what version you're on) did you clear the CMOS after verifying it was successfully flashed?

Changing GPU with new one - from Gainward RTX 2060 Ghost to ASUS DUAL RTX 2060
Run DDU to remove all GPU drivers(Intel, AMD and Nvidia) in Safe Mode, then manually install the latest GPU drivers in an elevated command, i.e, Right click installer>Run as Administrator.

I also noticed that the BIOS was reset after the shutdown
Do you have an grounding issue? As in do you feel a mild tingling sensation when you touch the metal part of your case while your bare feet are making contact with a tiled(non-wooded, non-carpeted) floor? Have you tried replacing the CMOS battery with a fresh cell?

Reinstalling Windows 11
Did you recreate the installer for the OS, installing said OS in offline mode and manually installing all necessary drivers in an elevated command while disconnected from the www? Were all drives disconnected except for the one you intended to install the OS onto?

RAM: G.Skill Ripjaws V (Black) (4x8 GB) 32 GB 3200 MHz
Does the issue crop up with 2 ram sticks on slots A2 and B2?

How are you cooling the processor and what sort of temps do you see when the issue crops up?

Changing PSU with new one - from be quiet! Straight Power 11 750W (died half a year ago) to Pure Power 12 850W
Did you replace the cables when you replaced the PSU's?