Guest cart lost after adding item

Having some trouble here. Trying to add multiple items to the cart in from a product page via a react component (using @cocart/cocart-rest-api)

All works great if you’re logged in. However as a guest, the api requests seem to behave correctly, but when you go to the cart it’s empty.

Immediately after adding to the cart, we have a cookie set for woocommerce_cart_hash, and woocommerce_items_in_cart. But I’m adding multiple items at the same time, and items_in_cart never increases.