Using a custom on off switch for Audio, but the audio for all layers playing at once!

I am creating a course without using the player, and have created a custom on/off button for the audio narration. I used a true/false variable that toggles the audio on and off. For the most part, this has worked out great!

But I have one slide that uses a slider connected to four different layers (each has audio) that show as the slider moves across. The audio works fine if you don't mess with the audio on/off button. But if you turn the audio off and then back on, the audio for all four layers plays at once. I have not been able to figure out a way to make it just play the audio for the current layer. 

Does anyone have any idea how to make this happen? I have included a file of the slide to help illustrate what is happening.