Question Computer crashes with a CPU in "low" temps

Jan 17, 2020
Hi everyone, I've had some problems with a CPU going to it's max temp (around 75°) then crashing while playing games and today it escalated quite a bit, we're talking about an AMD APU A10-5800K using his stock cooler and with a few years of usage already, probably 4 or 5 (I'm not the owner), the build is one of those like "mini PCs" and everything is kinda cramped inside the case so it has to be open so the temps wouldn't rise so fast.

A little bit more than a week ago when I started to use it to play Path of Exile the CPU would just sit between 70 - 76° while playing and then it would shut down so I decided to change the thermal paste and see if it would help, it's not some quality paste like Arctic MX4 instead it's some @*#! low quality product made in the country that there was in the house, even though it helped a bit, temp still was kinda high (65 - 71°)

Today while playing it crashed, something that didn't happen in a while but what changed now was the fact that the computer wouldn't boot, I tried taking one stick of RAM out and it booted like that, had some small programs opened at first like Discord and Firefox and it crashed again. After a while cleaning inside the case, seating up everything again and the computer still not booting I decided to clear CMOS using the jumpers in the motherboard (this one doesn't have the small round battery).

PC finally booted, everything seemed to be fine but now it seems to be crashing at like 40-50° and I have to reset the BIOS settings again, I had it load with the "optimized" settings the first time, now I tried changing the fan speed to full speed and it got better but not that much honestly, also the temperatures were going up inside the BIOS marking 81° (how??) If it was my computer I would have bought a quality thermal paste and replaced the stock cooler long time ago so, are there any solutions I can try?