Articulate Storyline Slide with multiple buttons and layers not working

Hello Heros,

I have a Articulate Storyline slide with 4 layers and all have audio. There are 4 buttons linked so that when the user clicks a button, it goes to the corresponding layer. I want to advance to the next slide once all 4 layers have finished playing in their entirety. I have set up the base layer so that the user cannot click a button until it is finished playing.  I also created a "Completed" state that changes the button's color once the audio is done playing on each layer. 

The Base layer works fine and I am not able to click a button until it is complete as I had hoped. The problem I am having is that the user can click on any of the buttons at any time to listen to that layer. I have set up triggers to try to prevent them from clicking on another button until that one finishes. It is not working.  Also, once the layer is done playing, it does not change to the completed state as I have it set up. Any thoughts? I am happy to share the slide as I am sure you will need to see how I have it set up.