So basically it says that for product ID 38 with attribute ID 63 there is another entry in the "stock_available" table but it needs to be unique, if it happens when you change an order status it means that changing the order tries to update some stock information and instead of updating it tries to insert in that table. This MIGHT still be caused by a module hooked to the order update process - did you disable all custom modules? 3. Probably it is some code that is triggered in this specific case, unfortunately i can't find any log with any error except the red banner showing what i posted. The fact that the error still exist even when i disable all the override and all the non native module, have me thinking that is something related to prestashop core and not some module. It would be nice to try to reproduce the error on a fresh install to see if it happen. I will try it as soon as i have some time.