I have problem with AwoCoupon.
Problem exist only if user is registered. So if you are a guest all works fine as should.
If you are logged in a website as registered put some item in the cart then you need go to cart checkout.
In check out there you need try delete remove item from cart or update quantity of item.
It will not work, you will get just a message, product quantity is updated, or product is removed from cart, but item will still be in to the cart.
Then without touching anything you just reload page second time and item will update correctly, if you agean third time reload page item quantity will go back to old position.
Is strange error but is wery troublesome, for quick solution I disabled System - AwoCoupon in plugin.
Now check out work OK