Swift : Game Controller

I have written a support class in order to use a standard game controller with Swift apps written for the AppleTV

The Siri remote only supports two buttons [A] and (X)
the game controller has 4 buttons A[Y] and [B]

however [B] is captured by the app, which is fine, but then immediately exits the app (not a crash, this seems to be the default button action)
Does anyone know how to disable that action so the [B] button can be used solely by the app?