Problem: The mini-cart header/sidebar widget of my theme does not show the correct count of cart items when adding a Mix and Match assortment to the cart.
When using Mix and Match, ensure that your theme is using the WC()->cart->get_cart_contents_count() method to count cart items. If you don’t know how to verify this, it is good idea to share this information with your theme author(s). By default, Mix and Match assortment contents are not counted. A Mix and Match assortment will be counted as one item, no matter how many products it contains.