I've been having some trouble recently on my website. I've updated the cart code to group products by vendors when the items are added in the cart by the customers. Everything works correctly for the grouping function. But I've noticed that the quantities of the items in the cart page are randomly changing when I proceed to checkout. For example, if the first item in the cart have a quantity of 5 and the third item have a quantity of 8, when I proceed to checkout the quantities are randomly assigned to other cart items meaning that what the customer ordered at the beginning is totally different at checkout.