[SOLVED] is my power supply failing?

[rahulss]

my spec
i5 6500
16gb ddr4 2100mhz ram
gtx 1060 6gb
HDD x 2 7200 rpm
Samsung ssd 250gb
dvd drive
Seasonic sii12 620w
I am a game environment artist and I love playing games so recently I was playing red dead online and the moment the gameplay started my pc would shut down and even when I would do heavy work like light a scene in the unreal engine or 3ds max my pc would shut down, so I looked online and everybody said it might be the PSU at fault so I sent my PSU for RMA but it was denied as they said they found no fault in it.
so after my PSU returned I cleaned my whole pc with isopropyl alcohol, even components, and applied Deepcool 6.5mwk thermal paste so that there should be no heating issue, so I turned on my pc and started some stress test and it passed (it passed the test even before RMA), so it worked fine but then again it started to shut down on heavy work, so I swapped it with my brothers PSU and everything worked fine even cyberpunk ran on high and ultra without shutdown at this point I made a video of it for proof, later I swapped my PSU back and surprise its running games and heavy work nicely but only for few days,
this is what I have noticed - every time my pc shuts down on heavy load due to games and work, I would swap it with my brothers PSU for few minutes and back to mine and everything would work fine for few days then the same problem will occur again, please help me with I need definite proof that my PSU is failing so that I ask for a new one as all the other are fine, I have even done clean os install at least 10 times, even tried old versions of them.
why does my PSU works properly after I have done a swap for few minutes then stars giving the same problem again?
small games like meat boy don't shut down the pc but games likes cyberpunk do(or any other heavy games)
is it the sign of failing PSU that works sometimes and sometimes doesn't.
please help as I am unable to work.

 

[refillable]

That doesn't sound like a PSU issue to me, have you tried using your brother's PSU for a few days and see if things work as intended?

 

[rahulss]

That doesn't sound like a PSU issue to me, have you tried using your brother's PSU for a few days and see if things work as intended?

i am going to install his psu today and try it for few days and see how my psu does in his pc , his system hi better than mine

 

[rahulss]

That doesn't sound like a PSU issue to me, have you tried using your brother's PSU for a few days and see if things work as intended?

i have been playing

That doesn't sound like a PSU issue to me, have you tried using your brother's PSU for a few days and see if things work as intended?

I swapped my PSU with my brothers PSU, he is playing Hitman 3 on ultra even his pc is powerful than mine but there is no issue, and I am playing medium the horror game on the high graphic and I don't see any issue either does that prove that there is nothing wrong with my hardware, then what is the problem. why does it shutdowm if i use my own psu. HIS PSU IS 550W AND MINE IS 620W.

 

[refillable]

That should be the proof, if your PC is running fine with other PSUs for days, that is a definite sign that there is something wrong with the PSU.

 

[rahulss]

That should be the proof, if your PC is running fine with other PSUs for days, that is a definite sign that there is something wrong with the PSU.

but my psu is also working fine in his system too what about that

 

[refillable]

but my psu is also working fine in his system too what about that

No shutdowns after days of operation?

 

[Vic 40]

Which motherboard? Might be that motherboard sensors detect a too low voltage and make things shut down, Like Asus with their "Anti Surge".