I too have been using X10 since the BSR days in the mid 70's and I am desperately trying to continue doing so.
I have almost a 100 devices spread over three house codes throughout our 2,000 sq/ft 3 story house and a detached studio almost 100' from the house and they have simply "worked" over the decades...
...until the introduction of LED lighting. We are in a semi-rural area and we are the only home on our transformer, so, we have not been subject to interference from adjacent homes. I ran into, and addressed, some distance issues when we built the studio in 2000, but really wanted to be Eco-responsible and have introduced first halogen, then CF and eventually LED's over the past couple of decades and it's clear that LED's especially are X10 hostile.
The clearest example was when I replaced the 10 florescent tubes in my shop with LED tubes and effectively lost the ability to control almost half of the X10 units despite a high end phase coupler/repeater. Turn the shop lights off, and everything X10 works. Somewhere someone described LED units as "black holes that suck X10 powerline signals."
I'm still trying, experimenting with boosters, filters, etc with limited success. I've trained myself to religiously turn off the shop lights every time I exit the shop, and I am hopeful to be able to continue.
The alternative options have serious limitations compared to X10, including the ability to introduce serious malware and privacy problems inside of strong firewalls. Nothing I have found has my favorite "ALL OFF" command that I use more than any other.
I need all the help I can get.
Beverly Howard