Hello
That is a strange problem, it should work with any of the soundmodules.
The reason for using SMT is that you get a diffrent enginesound on that module, SMX doesen't have that function. I dont care about that sound so i went for the SMX, and it's just plugged in to S20 and reciver no direct connection with the BMA.
Sorry i cant help you but i have posted the question on both the norwegion and swedish forum. Hopefully they can answer
