Hi All... thanks for all the advice.
I was able to get this working consistently without a phase coupler. I just created an "echo" program on EISY that sent the commands twice more. So that whenever it sees X10 on it does wait 1, x10-on, wait 1, x10-on. This works consistently. I think the problem is noise from my LED outdoor fixtures when they're ramping on/off, and noise filters didn't help. I wanted to turn 3 circuits on together. All works now, albeit with a slight delay.