Re: Sometimes violence is the only answer
"a standard “fix” for our standard original IBM XT and AT PCs - Any that misbehaved were switched off and carefully raised ~2cm above the desk by lifting them with a hand on each side, then dropped"
XT's were notorious for dry joints, so that explains that one.
ATs and others with that horrible ceramic 286 had problems with the socket fingers losing spring tension over time due to the heat of the processor (I left a burned on fingerprnt on one as a momento once) and there was a reasonable amount of thermal creep due to heating/cooling cycles. Shocking them was the best was of making sure you had a good electro-mechanical contact.
The best mod you could do to an AT was a heatsink and fan.