That was also a possible culprit. I noticed that one side looked pressed in (pad closer to the brake. Even if it was not the cause, I decided to make it symmetrical. T#1 the nut was very tight; #2 after I adjusted the one side to match the other, I had to re-center the brakes as they were now over tensioned toward the side I adjusted. While it made the most sense that the brake could have been pressed out, the fact that it was centered before, leads me to believe it had been uneven for quite a long time.