A machine experienced RAM trouble: https://forums.opensuse.org/showthread.php/547390-Puzzling-Keyboard The issue got fixed a year ago and its owner operated it without any annoyances for nearly one year.
The machine (ASRock H81M-DGS, i3-4130, 2x4GB RAM DDR3) started random segfaulting a few weeks ago. The user brought in the box for trouble shooting. Replacing the 2x4GB by 2x8GB killed the second memory slot. However the system worked reliably with a small performance loss using 1x8GB.
When the user picked up the machine and booted at his home it worked for a day. When being turned off and turned on again, the machine was dead: The fans would start and run for a minute, the turn off and start again, the loop continuing forever without even loading UEFI.
The user brought in the machine again. I cleared CMOS, installed grub and the machine was fine again. The user picked up the machine, turned it on at his home and the machine was dead again. This started a completely reproducible loop: The machine worked flawlessly at my home, but died when booted at the user’s home.
Replacing the ASRock H81M-DGS by a BIOSTAR H81MHV3 made the machine great again.