I've seen this before. Moisture from humidity (or from a spill) can cause mold or fungus to grow on a circuit board. Ordinarily a game console will run fine after it's dried thoroughly, but it's possible for there to be enough organic material left over to cause a short. If the circuit is forgiving enough, this would be enough to be the equivalent of a jumper resistor. Once had a VMU with this kind of problem, from being dropped in barbecue sauce by the previous owner.
If you think of all the coffee, cola, and chips that people handle whilst gaming, it's hard not to be disgusted at the idea of what you might find attached to a used game or a used console.
-KKC, who has nothing useful to contribute in answer to the original question of the thread. :)