Opencart 3 - "You must select a shipping method" error?

Question

opencart

Opencart 3.0.3.3

When placing an order, the error "You must select a delivery method" appears (the methods themselves are displayed on the page in the video radio-button and are selected by the user). But when submitting Ajax , this wicked error appears.

HOWEVER

1) The price of the products is NOT 0 ,
2) Delivery is required in the product is "yes"
3) Delivery modules are enabled 100%
4) Ajax sends exactly the checked delivery method
5) "All regions" is selected in (native) delivery modules
6) Regions , countries, geo-zones did not delete (only renamed Russia to Russia, its region and city, that is, transliteration)

in the file catalog/controller/shipping-methodthere is an error text that is returned by json-"om" - this is " error_shipping " But error_shipping is returned twice in different checks,

in my case:

if (!isset($this->request->post['shipping_method'])) {
            $json['error']['warning'] = $this->language->get('error_shipping') . '222'; //добавил 222 для проверки здесь ли ошибка, выяснилось что не здесь
        } else {
            $shipping = explode('.', $this->request->post['shipping_method']);

            if (!isset($shipping[0]) || !isset($shipping[1]) || !isset($this->session->data['shipping_methods'][$shipping[0]]['quote'][$shipping[1]])) {
                $json['error']['warning'] = $this->language->get('error_shipping') . '111'; // ошибка здесь 
            }
        }

I can't quite figure out the error.