Starting about 30 hours ago, my PC of several years began randomly shutting down or going to sleep unprompted. this was accompanied by laggy keyboard and mouse inputs, including symbols being typed that i didn't press. I noticed the issue seemed to happen more under load. I ran a diagnostic on RAM, system files, Storage, all of those seem to be fine. CPU and GPU temps never went above 50 degrees celcius and were generally at around 33, including when these random shut downs happen. I have the machine on a maximum performance power plan, basically all of those settings optimized for peak performance.
In the event viewer it says that the PC's power button was pressed when these sleeps/shutdowns occur, even when I disabled the power button in the command prompt. I have also starting today had the Event 41, Kernel-Power "The system has rebooted without cleanly shutting down first. This error could be caused if the system stopped responding, crashed, or lost power unexpectedly." followed by Event 172, Kernel-Power "Connectivity state in standby: Disconnected, Reason: NIC compliance"
I thought it might be the PSU so i replaced it with a higher capacity one (the one i had was a little underpowered for the gpu I got after upgrading my setup from a 1060 to a 3070ti, so i figured maybe this was a psu issue) sadly the issue persists. All the old psu cables were also replaced with the ones from the new one. I swapped out the motherboard battery and ran a bios update. for a bit i thought updating fixed it, was able to work under load for a while, but it keeps powering down. There was also no visible damage on the motherboard from what I could tell, no scorched or smokey anything, all capacitors look fine. The CPU and GPU also seem to be doing fine, I filmed task manager and coretemp while i was running the pc so i could see if there were any spikes in temperature or power draw during the shut downs. honestly it seems neither is the case, they seem quite random. I also tried plugging the PC in a different outlet than the surge-protected one I've used for years, seemingly no change.
Here are the specs, any help would be massively appreciated:
Asus Prime B450M-A motherboard
Ryzen 7 5700x cpu with aio cooler
MSI Ventus 8GB gddr6x 3070ti gpu
4×8gb ddr4 ram
OS is windows 10 on an nvme, then got 3 other ssds installed
Power supply is a BeQuiet! 1000w gold certified model, before that corsair 650m
Some extra points worth noting: I've now been able to work in hardware intensive tasks like photoshop and blender for several hours without crashes, but they do seem to happen sooner or later. I also tried booting the system in safe mode, the problems still occured. I am going to attempt to remount the RAM and see if that helps. If not, I don't have a spare motherboard around to test, but I suspect that it is the culprit and will probably need replacing