I have some lamps in my bedroom that simply will not regularly turn themselves on and off via X10. I moved plugs around yesterday and spent some time looking for something sucking signals or generating noise, but just didn't find anything like that. I am the proud owner of the monterrey instruments X10 signal analyzer so I am able to measure signal level and noise and there just wasn't any noise to speak of. THe signal level however was very interesting. In most places the outlets in a room are daisy chained one to the other around the room. The first outlet below the switch box in our bedroom had a signal level of .3 volts, which is excellent. 4 outlets around the room where the lamps are plugged in the level was down to 13 millivolts and the X10 module couldn't see it at all. I unplugged everything between the first outlet and the last and still it made no difference. It did bounce around a little though. Wiggling plugs and moving them around let me get the signal up to 20 millivolts and the module would sometimes be able to read it.
While doing this I took a good look at the outlets. They are the cheapest kind you can buy. They are all loose in the boxes. They are likely wired via the "backstabbed" connections and the screw then used to send power to the next one in the fastest and worst install method possible.
I will be replacing them soon. Backstabbed connections should never be used if you're concerned about your safety or about your X10 or other remote control signal quality. Screws can come loose too, yes, but if you torque them down properly they wont. Plus I can check them all again in 10 years and tighten them up if necessary. The backstabbed connections cannot be tightened up and just get worse and worse.
The way I'll be installing them will be via wire nuts, pigtails and the screw connections on brand new, high quality outlets. In each box, for the most part, you'll find the power inlet romex, and the romex carrying the power on to the next outlet. Those should be properly twisted and wirenutted with a short pigtail of wire. The pigtail goes to the screw terminal on the outlet. Doing your own outlet replacement isn't hard, it isn't complicated. Go get the little book the hardware store has on how to do it properly and safely. And obviously, if you're considering that you might be able to do it with the power on, or if you think you dont need to check each outlet with a voltage sensor because often one outlet in a room is on a separate circuit then you shouldn't be dreaming of doing this yourself. Most electricians will be happy to wire your house to your specifications. They will just charge you more hours of work if you make them use the good methods which take a few extra minutes per outlet.