early 1990s. IBM AT. At a workplace this computer would randomly freeze.
Wasn’t my job to do computers but I knew them
Had a hard time reproducing it. On a hunch, I installed GEOS which I knew would tax the machine and force the error to show its hand.
It would freeze the exact same moment during installation every single time
It would draw a graphic screen and stop 3/4 of the way down down to the same pixel
It hit me! Video! Hercules graphic board was bad. Had to be. Triumphantly went to the store got installed a replacement and everything worked after that.
And the old Hercules board?
One of the long series of memory chips had a slight bubble.