When you add a product to the cart in one language, then switch to another language and add the same product to the cart again, it will be displayed twice or you will get a fatal error.
The issue appears when using WPML, WooCommerce Multilingual and the Mix ‘n Match Products plugin from WooThemes. When the mix and match product is created and then translated, it is possible to add it to the cart twice in two different languages.
Doing such an action will result in having the same product visible twice in the cart or getting a fatal error. The result depends on the language in which the product was first added to the cart.
A product added in one language shouldn’t be added again in a different language.