Which component is dying?

[Exaco]

Hello everyone, i am posting here because im not sure in which section i should post.

History:
I've tried to remove some plugin files that's not related to OS, downloaded software called "Unlocker" ( that one with magic wand icon ), so i've unlocked all system files, while searching for leftover files my Monitor turned black, after PC restart it booted to desktop but instnatly i got "Graphics Driver Failed to start", i've installed DDU, removed the drivers in safe mode, downloaded GeForce Experience - even it was failing to instal.. So i thought okay my GPU died again, but i've suspected the unlocker which might messed my OS pretty bad, so reinstalled windows and everything works fine.

Couple days later i've experienced Freezing on idle e.g. when im writing comments etc.
After restart the PC gets stuck on BIOS screen ( the one that says press DEL to enter setup etc ) - Nothing responds.

I've read some stuff on my mobile phone what it could be, found it can be cause of RAM, so i removed one stick and it works fine, tried to insert the stick back, again wont boot, removed - works fine.
Later after few hours i get same thing ( Freeze, stuck on BIOS ) so i replaced the RAM to another stick - works again. Which means the RAM is good.

So the freeze might come back again anytime soon.

Which component could be dying? 
The motherboard already has fried Ethernet port.

Specs:

PC Hardware:

CPU: Intel® Core™ i5-2320
GPU: ZOTAC GTX 980Ti 6GB AMP! Omega
RAM: 16GB Corsair Vengeance® Low Profile
MB: GIGABYTE H61 - GA-P61-S3
SSD: Samsung 840 EVO 120GB
HDD: Western Digital WD Green 2TB
PSU: OCZ 650W 80+

Temps: OK
SSD/HDD Health: OK
PC works now: Yes ( without one RAM Stick )
BIOS settings: OK


Issue that still persists: https://linustechtips.com/main/topic/744191-mysterious-boot-problem/?tab=comments#comment-9428830

['ospis12]

Well, RAM can be faulty, with 2 sticks you increase chances that your PC will run in to problems faster. Cause you put more strain on to IMC

 

Unless you run memtest type software, it is not surety RAM. Try testing RAM, I know, it will take some time.

[Exaco]

9 minutes ago, 'ospis12 said:

Well, RAM can be faulty, with 2 sticks you increase chances that your PC will run in to problems faster. Cause you put more strain on to IMC

 

Unless you run memtest type software, it is not surety RAM. Try testing RAM, I know, it will take some time.

I tested one stick already, but i will try with two of them, hopefully it will boot somehow. 

['ospis12]

Have you tried testing both sticks in one stick configuration?

[Exaco]

1 hour ago, 'ospis12 said:

Have you tried testing both sticks in one stick configuration?

Just did that with Win Memory Diagnostic tool, set it to Standard and increased it to 5 Pass, no errors. 
Currently im with both sticks installed.

['ospis12]

can you try this test https://www.memtest86.com/ ? It will run outside windows,

windows is known to have not really good memory stability test

[Exaco]

5 hours ago, 'ospis12 said:

can you try this test https://www.memtest86.com/ ? It will run outside windows,

windows is known to have not really good memory stability test

[Astarore]

This may sound stupid but have you tried to run any sort of antivirus or Malwarebytes for example? 

[Exaco]

1 hour ago, Astarore said:

This may sound stupid but have you tried to run any sort of antivirus or Malwarebytes for example? 

Like i've said i've re-installed the OS and then the freezing happened on even fairly fresh OS. It was clean reinstall.
+ I've mentioned that it even stuck on bios so it clearly has nothing to do with OS/Viruses.

Since these issues is mysterious for me, almost dying and then getting fine again, i suppose it could be failing PSU or maybe even some spider went inside and shorted something slightly on the motherboard or PSU.

['ospis12]

Is it possible to you to test different motherboard and PSU?

[Exaco]

20 hours ago, 'ospis12 said:

Is it possible to you to test different motherboard and PSU?

No. But the PC is stable again.

[Exaco]

Update: 
Today it happened again, i've removed the RAM it was still failing to boot, i've noticed the Bios splash screen changed to old one when it was getting stuck on it, i've played with the ram by removing and replacing it then i successfuly booted the PC to desktop ( the bios screen was updated again ). 

Later after some time i've decided to put another ram stick back, it worked for like 5mins and i got BSOD "BAD POOL HEADER", PC automatically turned off and started to loop boot, i've removed the RAM and it works again..

So it seems like the motherboard is failing, right? Or it's the RAM that causes the failing?
Too bad i can't test it, because it's not that unstable usually, sometimes it works for days and sometimes it's not, so it would take months to test what's the problem and one of my friends clearly not gonna borrow me a PC for that long.