My system seems to crash from time to time. I still don't know what causes it.
If I leave it untouched for a few hours, sometimes, it crashes.
To resume, I have to force a reboot by unplugging the power cable (not even pressing the power button for N seconds seems to work).
Then, it seems to work just fine (after displaying some error messages about lost or orphaned inodes at boot). Until, one day, it happens again. When? I never know. It seems to follow some strange and unpredictable pattern.
Only when it’s idle for a while? That would point to power saving or suspend. You could try changing those to see if it affects the situation.
That's my feeling as well. It's set to suspend after 20mn and the power button in set to suspend, so maybe if I try to suspend and wake back up several times, one of the times it will fail... God! I am really not in the mood for that!... Let's see...
But yes, hardware. And I would suspect the display controller in particular. I’ve seen many that glitch when in power saving.
I can't remember when I bought it, it must be newer than that, but concerning the "bargain bin prebuilt" status... It certainly was cheap. That's why I bought it.