Online Store is absolutely useless

I tried purchasing two different items on different days, it shows stocks available at certain stores, I will add the product to my cart and then go to checkout and then get this most annoying message "Uh-oh! While you were gone, a few things have changed"

Why the hell take me to the checkout page if there is no stock, when I got back to check, it still shows some stores still have stock, just a waste of time.