Question PC build shutting down PSU overheating need advice on airflow pattern to fix this

[JonasTechButchery]

So I built this PC for my friend and it's shutting down in his place of work but not at my place under continuous load. Passes every benchmark... I suspect his place has +temp inside.
i5 (RX GPU 100w) 400w psu (real 400w with two 12v branches 180w each) ssd+slim hdd no optic device.

Shutdown pattern: On Valorant once per 3 hours, on LOL every 30 minutes. Power saver windows mode = no shutdown but low fps. -60% fps...

Now here is the kicker. The PC case is the small type compact tower 15 inches x 12 inches by 7 inches... with PSU being on TOP... in taking the hot air from CPU...

Naturally I max stated the CPU 80% so that to max temp is 55 degrees during gaming... just in case... GPU I also underpowered to max temp 62 degrees sapphire with huge coolers.

The air coming from exhaust 80mm is hot, the air coming from PSU is super hot after a while but no shutdown at my place only his. Tested the PSU in different case it's perfect works fine also opened it and checked the capacitors they are perfect. So it's not the PSU itself (I think) but the air it's breading in from the CPU raising temperature inside PSU beyond level of tolerance (I suspect)
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Now the case he has got SEALED top no airflow there and glass panel on side. I only use one exhaust fan since the PSU acts as exhaust itself... PC case exhaust slot fan is 80mm maximum size...

Should I perhaps 1) Swap exhaust for intake so that it blows on CPU and pushes some of that hot air towards front of case where I would place an exhaust 120mm instead of intake?
downside of this would be PSU would steal most of that fresh air like a thief leading me into the unknown zone. No idea how this would affect the build/airflow.

2) Put weaker thermal paste and bigger cooler on CPU in order to contain heat generation. + Add more powerful intake fan to mix mash fresh air with that hot air and make it cooler overall? This has a downside, too much positive pressure will send some of that air down on GPU... there is no other place for it to exhaust... very cramped case.
"star solutions raptor storm case" with glass panel side version.
3) Any better Ideas 😀? What is my best bet?

Swapping expensive parts is not an option. Just fan arrangement, type, quantity and CPU heat sink paste...

 

[Lutfij]

i5 (RX GPU 100w) 400w psu (real 400w with two 12v branches 180w each) ssd+slim hdd no optic device.
When posting a thread of troubleshooting nature, it's customary to include your full system's specs. Please list the specs to your build like so:
CPU:
CPU cooler:
Motherboard:
Ram:
SSD/HDD:
GPU:
PSU:
Chassis:
OS:
Monitor:
include the age of the PSU apart from it's make and model. BIOS version for your motherboard at this moment of time.

Ambient room air temps in both the abode and the office?

Swapping expensive parts is not an option. Just fan arrangement, type, quantity and CPU heat sink paste...
This would indicate that you're purposely creating boundaries when probably your best option might not even be fans, but the way the case breaths/ventilates itself.