I want to share this as an FYI & possible bug. Another one of my team members encountered the same issue. I created a project with many videos inserted on slides. On a slide later in the project, the user had the ability to click and reveal another layer. When the layer appeared, sound from the video on the first slide in the project played. My current solution (though I am not 100% sure it worked due to intermittent nature) was to insert a slide at the beginning with no sound-- just a button to jump to the next slide. I assumed this would prevent a layer from drawing sound from the first slide later.