There could be a problem with a Smarthome Insteon and Icon Dimmer Switches. Using the X10 Primary Address you can program into them.
Locally turning them on and off sends the proper on and off back to the power line. They turn on and off fine with commands from AHP.
The problem is how they handle a local bright or dim back to the power line. They do not send the stream of bright or dim signals. When the paddle is released a %Preset Dim is sent. I tried every lamp switch that AHP has and none showed the slider going to the dim level the switch was locally set to.
If dimmed to 0% or brightened to 100%. An Off or On was sent and not the %Preset Dim Command.
AHP could set the switches level using the older Full On, then dim stream to set the level.
Picking the LM14A, that sometimes works, did not work as it sends Extended X10 data the Insteon or Icon switches can not process for dim level.
Tests done with AHP with CM15A and line signal monitoring with a Smarthome 1132CU Controller with Smarthome Manager Essentials. In the Advanced Signal Test Screen.
The relay version that don't dim. Send an X10 on and off when locally controlled.
Smarthome had a Q&A entry on the differences and it jived with what I found.