How to get discounts in add2basket via ajax for unregistered users basket?

Question

1C-Bitrix

The code does not give prices with discounts from unregistered users.
There are no restrictions in the rules for the operation of the basket: in the restrictions tab -> User groups that the rule applies to: All is selected.
Moreover, the code works in the component, if not accessed through AJAX. It seems to me that something with the session.

$uid = \Bitrix\Sale\Fuser::getId(true);
$fullBasket = Sale\Basket::loadItemsForFUser($uid, SITE_ID);
$discount = Bitrix\Sale\Discount::loadByBasket($fullBasket);
$discountResult = $discount->calculate();
if ($discountResult->isSuccess()) {
  $BB = $discount->getShowPrices();
} else {
  $BB = false;
}

Revealed that the discount does not come after updating or creating a product.
And after removing $item->delete(); - the discount remains.

if($type == 'update') {
     $basketItems = $basket->getBasketItems(); 
     foreach($basketItems as $item){	 
        if($item->getProductId() == $productId) {
     $fields = [
        'QUANTITY' => (int) $quantity
            ]; 
     $item->setFields($fields);
  }
    } 
    $basket->save();
}

$basket = \Bitrix\Sale\Basket::loadItemsForFUser(\Bitrix\Sale\Fuser::getId(), $site_id);
$discount = Bitrix\Sale\Discount::loadByBasket($basket);
if($discount): //discount пуст (
    $discount->calculate();
    $discounts = $discount->getShowPrices(); 
endif;