Curious that the LM14a interface doesn't work for you. I've used it with both my HCM06 series (true rocker) and the older 6381 series switches.
Do you happen to have a repeater in your installation? If so, it's possible that the repeater can't repeat the extended codes. If your Leviton units are on the opposite phase from the CM15a, they might not be able to receive the transmission.
What model Leviton units are you using?
My Leviton switches are all true rockers. I believe the 10-year-old ones are the 6381 series, with the physical address wheels and red LEDs. I also have one of the newer models which replaced those, with a green LED and software address setting.
Yes, I have a SmartHome dryer-plug repeater. (A passive coupler didn't do the trick.) So you have probably nailed my issue. But I'm satisfied with having the timer call a macro. It's easy and it works.
Finally, my
really old X10 brand cheapo wall switches are starting to die. They are responding to addresses other than their own and/or not responding to their own addresses. This annoys the hell out of the wife (and me). My problem is that the two worst offenders, following Murphy's law, are behind a monolithic piece of furniture which would have to be disassembled.