Richard,
After some more testing here's what is happening. This happens when I'm playing in the middle of the day, at night, or with an overhead light on or off. I'll play for about 10 minutes and everything will work perfectly, but then all of a sudden, the drums on the right side stop triggering. But, if I hit those drums with my LEFT hand, they do trigger. I've tried hiding both sensors behind my knees for a few seconds and that often brings them back, but not always. Sometimes if I just keep playing, they come back on their own. Other times, I've had to quit out of play mode, go to the lighting section, and it shows my two feet, and my right hand (red), but there is a little white dot where my left hand is that moves with my left hand, and the blue circle is on the far left side not reacting to any movement. I hide the sensors behind my knees for a few seconds, and then the blue and red circles sync up just fine. I can then go into play mode and play for 10 or 15 minutes, and then it happens again. What's strange is that it seems to happen randomly. I would think if I had some sort of reflection or lighting issue, that it would be unable to work perfectly for a while with no problems at all. I have tried not using the app, using it on my iPhone, iPad and Mac but that doesn't seem to make a difference. I did notice it happening on some of the pre-set kits, and I haven't yet tried creating my kit again fresh, but that's next.