Prestashop 1.7.8 - Products out of stock but customers sometime still can place order

[still]

Our online store is built with Prestashop 1.7.8. We have a problem that some of our products are out of stock but customers sometimes still can place orders for these products.

We have tried all different browsers, different devices and times but we can't replicate it by ourselves, but our customers place out of stock orders almost every day.
 

Allow ordering of out-of-stock products is set up for NO

For stocks management we use: https://addons.prestashop.com/en/fast-mass-updates/41453-product-bulk-edit.html

Do you have any ideas how we can solve this problem?

[Piotrabs]

We have the exact same problem with some orders. We double checked the order process (even set up product to 1, added to cart and then set it to 0 to see if that may be the case of caching).

We can't replicate it but customers can sometimes order products with 0 quantity... the first one is that person ordered 1 thing, next to it is quantity of that product... even on our CRM the quantity is 0 these are updated from that CRM.