My site: http://www.vibrationist.com/marinaj/#!/store/products/pearl-necklace/
I selected the "image is pre-selected" radio button. I then used the shortcode on my edit page to point pinterest to a specific image URL for the above post. The top pin it button is the one from the shortcode because it is able to use the specified image. The lower pin it button is whatever the plugin default was and it's not turning off.
Of note is that I'm using Marketpress and the page in question is a product page. I have the latest version of WordPress.