Hi, I had this issue and I noticed others did as well when multiple instanced of WPaudio were included on the same page.
When you play an item to completion, then play another item, the completed item restarts and plays as well.
I figured out this was because the 'wpaudio-playing' class is not removed from the player when it finishes playing the file.
Here is the fix, go to line 223 of wpaudio.min.js and you'll see:
After this, but before the closing bracket, add:
// Fix to remove "wpaudio-playing" class when end is reached if(info.position == info.duration) jQuery(elem).removeClass('wpaudio-playing');