Storyline 360 Modern Player Progress Bar - Rewind

It seems the progress bar works fine in the modern player with only one layer.  A user is able to move forward and backward, basically backing up to a point and resume playing from the point of choice.  But, when I have a second layer the user is not able to backup to a point prior to the layer's entrance.  The only choice for the user is to replay the slide using the reply icon.  I do have music on the this slide that plays through both layers.  Any help would be much appreciated.

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