If the add to cart popup is enable:
If you add a product and the popup appears and you press either the view cart or continue shopping too quick the product sometimes does not get into the cart.
Turn off the popup and it always adds. Must be a cookies data transfer issue. Tried using IE11, Chrome and Firfox.
Found temp fix by introducing a 2 sec delay in popup file padded.php found in components/com_virtuemart/views/cart/tmpl.
Also tried with cache disabled.
* @version $Id: cart.php 2551 2010-09-30 18:52:40Z milbo $
//sleep for 2 seconds
// Check to ensure this file is included in Joomla!
defined('_JEXEC') or die('Restricted access');