I guess that you don’t need to worry about that. The problem is that when you click on “Back” in the browser it returns you to the checkout page and don’t reload it (on iOS only). That is why it tries to load the data about your previous order with AJAX and can’t do this since the order is already complete. I think that your customers will not face this and hope that WooCommerce will fix it someday. 🙂

Regards