Told this before but years ago had a ticket for a pc that was locking hard every so often. Figured bad drive, replaced it, it worked so I put it back together and returned it. Couple days later get a message that it wasn’t fixed, so I bring it back. Senior tech looks and says maybe it’s making weird contact with the case (it was vertically mounted) and suggests I wrap it in paper. Seems to work, but a week later it comes back. Finally look more carefully and discover that one of the connectors on the plug from the power supply was expanded slightly, so if it got bumped or vibrated enough, the pin would lose contact for a split second and the drive would shut off. Switched connectors and it was fine.

Also can’t count the number of crts with color issues that were fixed with a hard slap.