Like garcianc2003, I wondered about the sub's auto on mode and a possible conflict with the signal being provided by the SMS-1. An easy test for that would be to set the sub to be always on and leave it that way for a few days. I'd also make sure the SMS-1 isn't in any sort of mode that would cause it to be shut down (such as the 12V trigger mode) or in Night mode (which creates an adjustable "partial muting" of the sub channel).