I have a curious one to report. I had hit the "1-OFF" button on the PalmPad in our theater room and nothing happened. So I dimmed the lights manually. After the movie the "1-ON" button didn't work either. Both work through a TM751 plugged into a nearby outlet, and trigger macros in the Ocelot. I didn't think too much about it at the time because that's how Alexa often ignored commands. But the next morning I noticed that our irrigation system wasn't working right (controlled by an X10 WGL Rain8 irrigation controller). Hmm...
I went into our utility room where the prototype XTBR boosts X10 signals on the X10 phase. Its green light was flickering constantly, indicating a continuous stream of potential X10 commands. I grabbed my XTBM-Pro prototype to see what was going on. It didn't detect any valid X10 commands, but it did indicate continuous .24V to .26V noise at 124KHz. While not directly inside the X10 bandpass, that is close enough to cause problems.
So I started flipping off breakers one-by-one and then back on. Two breakers caused the noise level to change, but the flickering of the XTBR's green LED continued. Then one breaker killed the noise and stopped the flickering. But when I turned it back on, neither the noise nor the flickering returned. There are no X10 transmitters on that circuit. I suspect some electronic device on that circuit started injecting noise onto the powerline, and cycling power restored normal operation. I wish the problem had returned when I turned the breaker back on so I could have tracked down the cause.
It has been over a week since that happened, and our X10 system is still back to 100% reliability