This is a Magento 1.7, I need some help or hints on where to look to solve this issue please, on the frontend of the store I add an item to the shopping cart, it take a while and shows the product as Out of stock and "Cannot add the item to shopping cart.". I look in the backend for the product and the inventory shows number 0 and out of stock, even when a few mins ago there was plenty of items and in stock. Any ideas on where to find a solution please? thanks.
looks like a custom module or external sync is updating your stock qty's. Maybe something is changed in this external system whereby the stock sync isn't valid anymore.
Does not look like default Magento.
A observer could actively be fetching external stock when a product is added to the basket.
Try to look and maybe temporally disabling a module and check if the problem persists.