We've created an extension that sets a default shipping method for the cart. Below $50 the shipping costs will be $5,95, above $50 the shipping will be free.
The function itself works fine, but the problem is that the amount for shipping seems to be cached (different than other cart totals).
If I have a product that costs $19,95, add this to my cart, and in my cart set the quantity on 4, free shipping should be shown. All totals are updated, only the shipping still shows the $5,95. After I refresh the page again, the shipping cost is update to 'Free'.
How can I prevent this cache?