It's not unusual for music to have a harder time triggering a sub's "auto on" mode - there's less low frequency content present when you remove the LFE track, unless you are listening to something like pipe organ.
Does anyone know of a way to adjust the LFM1-EX trigger sensitivity?
Best way is to turn down the gain on the LFM-1EX's amp and re-calibrate the sub trim in the processor. It will cause you to increase the gain on the subwoofer output, which will cause the sub output to be higher and make it easier to trigger the sub on.