A Devilish Problem With Maximus Xiii Hero And I9-11900k Q Code D4 And Its Reincarnation

Hello,
I rebuilt my workstation from 10 years old P9X79 WS to a couple of months old ROG MAXIMUS XIII HERO coupled with an 'Intel i9-11900K', 'Corsair VENGEANCE RGB PRO SL 128GB (4x32GB) DDR4 DRAM 3200MHz C16' and an 'Asus GTX 1660Ti...
The reason I have a new build is that towards its last days the old build it started to freeze... It was a hardware problem.
The first thing I replaced was my GPU card to DUAL GTX1660TI O6G EVO. Which is also my GPU card of the new build. And also a quite new purchase.
The problem I am having is 'White light' sometimes followed by "1 long 3 short Beeps"...
And Q code displays "d4" but the post continues after a while and it settles on "A0" And as the hard drive light blinks away, as the "White" light indicates a GPU error remains and no signal is received by the monitor.
This Q code 'd4' has started right away with my very first boot attempt. However, as I rebooted, it did not give any error on my second or on the third try. Which I kept the system on, almost for three days at that time. Then next day on the fourth booth, it stuck on GPU card error again. This is how it continued for six days.
And on that sixth day, after a successful boot, the system and the monitors freeze after a while! You know as my old build did! So, I rebooted again, it freezes again in a few minutes. And after that, I couldn't pass the GPU error; the "d4" and "white light" and the "beeps". Yet the post continues and the Q code finally displays "A0". Meantime, the GPU card shows a "White" light as oppose to a "Red" light and both mobo and GPU card illuminate RGB lights.
When the system was working I had many HDDs and an SSD installed, and a few USB-connected devices plus fans, all working fine.
Now, I just have an SSD and 8 fans. I have an i9-11900K cooled by a Noctua NH-14 with two fans. That's it. I even unplugged anything coming from the case such as USB connections and whatnot.
Now, I power the whole thing with a Corsair AX1200i PSU, and it is the only thing that I haven't replaced from my old system...
It shows the green light and seems working fine also monitored with its "iCue" app when I could boot. When the system was working I checked every component.
Rams were showing 64 GB instead of 128GB. I realize that two of them weren't properly placed so I corrected that and got 128 GB. I checked each Ram individually and they were ready for OC and they were showing proper voltage and everything. Same with the CPU. Each core seemed to be functioning normally. At one ouint it even OC'ed %10 with auto OC.
Even though I do suspect the PSU, I can't be a hundred percent sure if the PSU is really the problem...
I couldn't figure out which device was the faulty one with my previous system either. I took my system to three different shops for testing and none of them couldn't find anything wrong! Even with all the stress tests and whatnot, they couldn't even manage to duplicate the system freeze... And as soon as I get home, I get the "frozen screens" which they couldn't produce. Once even for a consecutive three days, they fished for the error and got nowhere...
So, as you can see it is weird luck I am having. It feels like this is a curse really...
I replaced the GPU card first and that didn't help. Nevertheless, I realized I replaced the wrong device. But maybe as the previous GPU card (Zotac) was faulty and with my bad luck, the new GPU card that I bought was/is also bad. Then, I end up replacing everything except the PSU.
I just don't want to buy a new PSU and find out that in fact, it was the GPU card that was the problem all along...
So I did two more tests today. First I removed the GPU card. Since I have the integrated CPU graphics. But I get all the same errors. White mobo light and beeps...
Then I managed to borrow a 600 watt Thermaltake PSU. I hooked up with high hopes that it would work and I can finally pinpoint the faulty device after all the drama.
But no such luck! I still am getting the same errors. And now the white light is accompanied by a Yellow light as well, indicating that something wrong with Rams too...
When the Corsair AX1200i was connected, and the white light came up, the yellow light also came up for a very short while, and as the post continues the yellow light went away as the white light remained every time.
However, with this 600 Watt PSU, the yellow light also remains and the post does not continue...
So 'd4' is the final Q code there...
This is even more confusing. I am baffled. Is it the new Motherboard that is the problem?
'D4' is explained as either integrated GPU, or if a GPU card is installed the GPU card is not detected or has a problem. So they suggest checking the CPU! But the CPU was working just fine a week ago. As all the Rams were...
I don't know where to go from here?
And if you read the whole thing I appreciate it, I know it's a lengthy one but so is my curse...

 

what a weird idea to put 5 minutes time limit to edit a post in order to fix mistakes?!?

 

You have 10 minutes to edit a post.

 

I beg the differ... When I clicked on edit, the message popped out stating that I exceeded the 5 minutes window...
Also, I should be able to edit after 10 minutes as well. That is the whole point, making mistakes and being able to correct them without a time limit...

 

Alsoı, all my parts are compatible. I did my research! Matter of fact, both Asus and Corsair gave me their blessings personally. Asus put some 128 GB Corsair rams that higher than 2333 MHz into their compatibility list after my request. The video card is also listed as a compatible device.

I also did reset the CMOS a couple of times.

I am running the latest BIOS. I updated the unit before running the system through Asus's USB port. The drivers were installed through the driver disk that came with the unit.

Nothing is automatically updated in my system.

 

Really? This is the only comment I get? How many minutes I was given to edit my post... Or how many minutes should I get to edit my post?
Or Should one be allowed to change things he/she said? Is it ethical to time travel? Am I in the right place?

 

Also, as an info UPDATE
My wiring is done by an engineer. I have 2.0 ohms ground provided by a fat copper rod buried under the ground 4 feet deep, connected to my system with a thick copper cable. The audio equipment is on a dedicated circuit. I have a superb power conditioner. (Which just in case I tried bypassing the UPS as well) So I do have a clean and balanced power in my studio.

I will do barebone tests and will come back ...

And I did manage to take a snapshot of the "you can't edit (5 minutes) is passed error" and attached it below...

 

I wonder where are these Geeks, that are mentioned?

Like anybody cares her is an update:

After a BIOS update that was just recently released, things got worse!

After the new BIOS, the post is stack on 'D4', and the 'White' GPU error, is now accompanied by a 'Blue' RAM error light...