Random blackscreen lockups while playing LoL/Sims 3

So, when i play League of Legends (or Sims 3) my PC sometimes gives me black screen and stops responding until i reboot it. For Sims 3 it usually occurs once in a few hours, not every session (been fine for the last couple of months, tho I don’t play it that much). For LoL – pretty much every session, once per hour or so. Crashed twice in my last game. And i am not sure if these problems r the same, but sometimes when i do other random tasks, PC freezes up for a few seconds then goes back to normal again. I have no idea whats goin on, and, tbh, im freakin out. Got a few opinions that it might be a faulty hardware, but i have no clue how to find out which one
There seems to be no pattern to when that happens, might be in a middle of nowhere when only my champion is present or during a heated teamfight. Or anything in between

This is what i tried so far (and it didnt really help):

Official Windows hotfix p95v2810.win64 (Issue there is described as: This issue occurs because of heavy group policy use and the presence of SCOM causing a deadlock condition between the Lsass.exe process, the Redirected Drive Buffering Subsystem (Rdbss.sys) driver, and the Winsock kernel)
Jumping between different GPU drivers (with/without DDU)
Various benchmark/stress tests such as Heaven (did just fine for a couple hours, then i turned it off) and Prime95 (2 hours, also fine, tho one temperature score* was 90+, so i didnt think its a good idea to let it run further when im not around). Have a HWiNFO-log for the latter. Memtest64 also found no errors.
Tweaking Radeon Graphic settings for both games
Checking power supply voltage in the BIOS, seems okay
Re-installing Windows with/without updates
Checking for malware, CureIt didnt find anything, there r also no suspicious processes in task manager
BIOS is also up to date
*As for cooling/temperature: aside from one mysterious extra-high sensor (marked as Temp2 in SpeedFan and Auxiliary in HWiNFO), others hardly exceed 50-60 even under a heavy load, so i am pretty sure thats not the issue

I do not have a bucket of hardware pieces just lying around, so I would really like a way to figure the issue out without swapping them. Thanks in advance

System:
GPU AMD R9 380
Win7 64 bit
Monitor Dell 22" P2217 (2217-4565)
Motherboard MSI 970A-G43
CPU AMD FX-Series FX-8350 OEM
Power supply 700W Zalman ZM700-LX
RAM 8GB

there are no dumps, and after verifier-BSOD PC refused to boot, so i had to use restore point. no dump either

the problem is, that its not exactly the BSOD, its a black screen that locks the computer up until i reboot it. so i probably posted it at the wrong section, but i really have no idea where should i go with that
im pretty sure i could "orchestrate" another blackscreen within like... a few hours, but it doesnt provide any information, so should i?

axe0 said:

How old is the hardware?

about 8 months, mouse is really-really old (like... 6 years mb?), but i dont think its responsible for the issue

axe0 said:

Please fill in your system specs

done
tho note that scarlett usb-sound card is not plugged in everytime, i only use it for work

axe0 said:

Could you reseat or seat the GPU into a different slot.

i would really like to avoid that if possible, itd leave me with a hole in my case that sucks up all the dust within 5 square kilometers
i dont think its GPU's fault anyway, but ill try playin smth heavy-GPU-demanding on it (will Civilization 6 do btw?)