Layers Audio Plays ONLY When Clicking on the Slide From the Menu During the Playback of That Slide

Sheesh! Did I just confuse you with that title? Sorry, let's see if I can explain. 

I'm building a project in Storyline 3 (actually a co-worker is). I have a slide with a voiceover on it and then 6 PNG files (icons) that show 1 of 6 layers when clicked. Each of the 6 layers has a single video on it. When you click on any of the 6 layers, that layer's video animates in, plays, and then animates out to the base layer when it ends. Once you've clicked on all 6 icons, a next button appears and you can move on to the next slide. Pretty simple, right? And all of this works just fine. 

The issue that we're having, and it's an odd one and may be a bug, is that if you happen to be watching one of the videos and decide to use the menu (along the left-hand side of the player) to click on the same slide, it goes to the base layer but this time it plays all the audio of all the videos, including the base layer's voiceover. We discovered this because as we were watching the video, we wanted to go back to the base layer to select a different video and the layers don't have a way to click back to the base layer. So, as a viewer, you intuitively select the slide again from the menu. And then, for some reason, the slide does an audio dump, but ONLY when you click on that slide when that slide is playing. If you click on it at any other time, it won't do the audio dump.

We've tried a lot of stuff. We've reset the slide to initial state, paused the base layer when playing a layer. Used triggers to hide layers when timeline starts. Changed the videos to play when clicked instead of automatically playing. And countless other things. A workaround has been to lock the menu so the user cannot click in it at all, and thus the problem stops. But I know there has to be a better way.