Cart update triggers after a second page reload

-- HikaShop version -- : 3.1.1 [1707101222] Business
-- Joomla version -- : 3.7.3
-- PHP version -- : 7.0.20
-- Browser(s) name and version -- : Chrome 59

I'm developing a plugin that adds a free product based on the current shipping zone. This works, however, it will only show the added product in the cart after a second reload. Changing the amount of initial products triggers it, but it does not show the newly added product in the cart. It's the same when removing the product again after changing the initial product amount back to a lower case (which is outside the shipping rules; the shipping changes when I change the amount of products).

The cart does update correctly whenever I update the amount of a product using a POST (pressing return/enter); it does not when I use the AJAX refresh button.

I'm using the event "onAfterCartShippingLoad" but I've tried other events aswell loading the cart dynamicly using the cart class. I'm using the following code to add to the cart;

$classCart = hikashop_get('class.cart');
$classCart->update($params->productId, $params->quantity);

This adds the new product to the database and the right card id, however, it does not show the product in the cart the first time its loaded. Are there any events that will trigger before showing the cart products but after the shipping has been updated?