Transitions markers/region stopping music - no sound after

I have a transition marker set up to go back to the start marker. Once the play head hits the transition marker, the music stops, four counts of nothing, then goes back to the starts but there is no sound.

The same goes for if I am using a looping and transition region over the same bars of notes. If I try to tranaition out of a looped region by increasing a parameter, the music stops.

What am I missing?