The EZX10RF works with both X10 RF and X10 powerline messages. Either X10 message source will trigger an Insteon On/Off message for the associated Group number. The ISY Event traces I’ve posted on both the ISY forum in getting the EZX10RF defined and this topic were generated from my MAXI controller so I could separate in time the House/Unit message from the House/Command message. The House/Command message triggers the generation of the Insteon Group On/Off message, the House/Unit message that preceded it way back when controls which Group is triggered. I think the X10 message segments from the alarm system are coming in a sequence such that the wrong Group number is being triggered. At least that is the working theory until we can see the X10 messages in the ISY Event Viewer. That should provide the definitive answer.
Thanks for keeping an eye on the forum and your responses. They are always helpful and appreciated.