Audio not playing on slide launch

I have a very straight forward project - no special triggers, single-layer slides where the user advances the slide with the built-in "Next" button.  Some slides have videos on them with audio tracks, some slides have simple narration tracks. Seemingly randomly, slides will play without audio. If you navigate back to the previous slide and then click back to the "problem" slide, audio will play. This has happened on several projects recently. I've logged this as a case and included my project file, and been told there's nothing wrong with my project and it plays fine. But this continues to happen to people viewing in Review 360.