It doesn't matter what the promotional materials for the devices you're buying say, you will someday encounter a problem. A list here of the things that we know cause X10 issues might help narrow things down. In most cases an inexpensive X10 filter on the offending device will solve the problem, but sometimes the problem is more insidious. It can be an interaction of 2 or more devices. It can be a device that maintains an internal battery and only eats X10 signals when it's charging once a day. It can be a device that only makes noise when warming up and then stops, or only makes noise when warmed up so just switching it off and on will make things go away for a while. There are ways and tools for figuring this out.