Shipping charge on bundle + extras

Hi team, our shipping strategy is priced based - free shipping for all orders over $150. However, when a customer adds a mixed dozen pack (product bundle) to their cart and then adds a couple of extra bottles to their cart, they are getting charged shipping. The total price is over $150 but the couple of extra bottles are under $150. Is this a bug or am I setting up something wrong in the settings? :thinking: