Many moons ago, X10 worked fine throughout the Convastor household. A mere 1318 sqtf + basement: Not all that challenging. But, over the years, as more and more electronic devices were added, X10 became increasingly unreliable. I'd added one-or-another passive phase coupler to the distribution panel years ago. Seemed to help
a little. Wasn't a night & day improvement. A few years ago I bought a SmartHome BoosterLinc repeater. It helped--when it wasn't off in the weeds. When it lost its tiny little mind it would make things
worse (I got in the habit of leaving it unplugged except when I set timers up [had to use two to reach everything] for an occupied residence simulation when we were away.)
Finally, a few days ago, ordered a JV Digital Engineering XTBR X10 Repeater. Ho-ly smokes! The thing is nothing short of terrific. Every X10 device in the house is now reached from every controller in the house. I even hit an appliance module out in the µBarn, 75 feet from the house and over 100 wire-feet from the distribution panel, using a controller on one of the worst circuits in the house.
Caveats: What worked for me may or may not work for you. In my case, my suspicion was my problems were probably
mostly signal suckers--things that reduce the power of X10 signals, rather than interference generators that were burying the X10 signals in noise. (This roaring success suggests I
may have been right.) And remember: I already had a phase coupler installed.
Now that X10 is again reliable for us, my plans are to probably acquire a Raspberry Pi Zero W and cm15a, and run PiX10Hub.