Played ~45 minutes of DDR tonight, after mowing the lawn this afternoon when we got home. One of the pads is only responding on the "back" arrow about 50% of the time, but I don't know if it's the pad or the floor. Given the state of this building, I wouldn't be surprised if it was a mushy spot in the floor.
I'll have to experiment with moving the pad around to different spots and so forth to diagnose the problem. If it is the pad, hopefully customer service will make with the replacement. We'll see!