Comment by pugworthy

I recall reading a variant of that where a terminal had a "print screen" button, and the claim was it would work when standing but not when sitting down (or was it vice versa).

In the end there were two print screen buttons, only one of them functional, and one of them more obvious when standing (or sitting).

These kind of stories are classic debugging parables that teach you to step back and consider what you may be assuming incorrectly when something absolutely doesn't make sense or seems impossible.