Because you are embedding multiple vizzes you should remove the dynamic script creation code for the Tableau js file and place it outside each viz script so it is only called once. I am not certain this is your problem but try this first.
I've been trying to implement this the way you've described.
Sadly I couldn't manage to include all the visualizations in this way.
I've resolved this by creating different HTML pages for each Viz, and importing them via <iframe>