Jack,
You might try the M10/P* / M11P* (off/on) commands. They don't have a time delay associated with them as M3 (other Ms?) do.
I don't know if you can use more than one output though, but you might try replacing the M3 first to see if it helps. I also haven't tried, but maybe also use E10/E11 commands for another output. If I am wrong, someone will hopefully jump in with corrections/another suggestion.
Regards,
John Champlain