Woocommerce API duplicated order item meta items when using swatches

Hi,
I use Woocommerce API (PHP client) to get a list of orders and give a possibility to update the order status from an external web service.
API works fine for products for which I do not use swatches.
In other case, updating such an order, results in that the attributes of the product for which I use swatches are duplicated in order (order’s item meta-data-array length increases with extra indexes containing same attributes duplicated).
I’m giving up witch this plugin…