I can confirm this was indeed the problem. When testing locally the player will not stop with multiple instances. When tested on a live web-server, it will only play one at a time.
Thanks vynnus!
I’m trying this and received an error:
Fatal error: Call to a member function on a non-object in /homepages/23/d236268553/htdocs/wp-content/themes/k2/app/modules/php.php(7) : eval()’d code on line 5
Is the K2 theme messing with it?