I have a light controlled by two "three-way" switches. It has worked properly for many years. It started getting a little flaky. I noticed that one of the switches needed to be pushed up a little harder for it to work. I replaced that switch (I checked the continuity of the old switch, and it was flaky). I got some of the functionality back, but not all. Then I pulled the other switch and it was bad as well. I replaced it and still did not get total function back. So, I pulled both switches off, and with no wires connected in either box and with the power on, found power going to each of the switches. I am baffled at how this could ever have worked. Is there any explanation other than I have some sort of short in my wiring?