I have a client using version 3.6.0 of the Smith cart that we developed for them.
I was informed by my main contact that users were still able to proceed to order a specific-sized shirt/product even though my client was out of that product size.
I did a test order to confirm, and I also did another test order on a different product that also had a certain size out of stock, and I was able to proceed with that order as well.
So, it looks like the cart is having issues with quantity tracking at the variant level or not informing users that certain sizes/variants are out of stock at the proper time of trying to place an order.
See the attached screenshots for one of my tests. The first one showing that one of the product variants is out of stock (at the store administration level), the second one showing the screen before you are able to successfully go through to complete your order.
I know that product variant inventory gets more attention in newer versions of the cart (though I can still enter product variant quantities obviously in this version), would upgrading the cart possibly do the trick (everything else works fine so I'd like to not upgrade if possible, for risk of messing up other cart features)?
Let me know if anything is unclear. Thanks for any assistance!