I had an intermittent issue many years ago, that I had a hard time tracking down. Certain switches refused to respond to commands at night - but were fine again by the morning. Hours and hours of troubleshooting within my home was able to identify the source of the problem. My dad suggested that I should look for things that were on at night, and off during the day (like outside lights), but I'd already ruled mine out as a possible source of the problem. Well, it turns out it was one of my *neighbor's* front porch lights that were the problem. Despite being across the street and one house over, we were still on the same pole transformer, and his one bad bulb was enough to knock out half my system. He's a good friend, and was more than happy to help me troubleshoot. First he turned off his porch lights, and I confirmed that the problem was gone. Then he turned them back on, and I confirmed the problem came back. Next, he left the lights on, and removed one bulb at a time, and found that one of the two on his porch was the culprit. He also noticed that when it was on, it made a buzzing noise that the other (identical) bulb did not. He was more than happy to leave that one bulb unscrewed overnight, and I purchased a pair of replacements for him the next day. I had similar experiences with other CFL blubs (I have 6 outdoor fixtures, all had CFL bulbs until they were slowly replaced with LEDs), where a bulb would start to fail and make noise over time. Each time, the noise got to a point that it crippled my system completely. Whenever I had system problems, those bulbs were the first ones I'd check (easy to do - just shut those lights off and test).