Very annoying check out

ok, my friend and I book together, we put trollfjoid in our cart, showed up as in our cart but when we checked out, we couldn't because an extension was sold out, even though nothing sold up as being sold out. After ten minutes and multiple attempts at trying to check out then it showed up as being sold out. It happened a second time to me when I tried again to check out. I finally removed a tour that I thought was the problem, lucky for me it was. Just be aware that having it in the cart doesn't mean that you got everything you wanted