WAIT. Waaaaiiit. I got it. Even trying with a new game, I got the same result. Even if an AudioX object is global, it cannot play sounds on a modal layout unless there's a copy of that object on the modal layout.
I had Layout 1 play autoplay resource every one second, with a modal layout object that had the EXACT same event going, linked to Layout 2. The AudioX object was on Layout 1. When you run the thing, obviously, the modal layout object's going to be stealing the show. There was no sound. When I had it close by pressing a key, THEN you could hear the sound effects. That's the best I could explain it. Hope that... makes sense.