diff --git a/vendor/magento/module-checkout/Model/TotalsInformationManagement.php b/vendor/magento/module-checkout/Model/TotalsInformationManagement.php
index 7328f884554..25e2f0ba4e0 100644
--- a/vendor/magento/module-checkout/Model/TotalsInformationManagement.php
+++ b/vendor/magento/module-checkout/Model/TotalsInformationManagement.php
@@ -5,14 +5,14 @@
  */
 namespace Magento\Checkout\Model;

+use Magento\Checkout\Api\Data\TotalsInformationInterface;
+
 /**
  * Class for management of totals information.
  */
 class TotalsInformationManagement implements \Magento\Checkout\Api\TotalsInformationManagementInterface
 {
     /**
-     * Cart total repository.
-     *
      * @var \Magento\Quote\Api\CartTotalRepositoryInterface
      */
     protected $cartTotalRepository;
@@ -42,7 +42,7 @@ class TotalsInformationManagement implements \Magento\Checkout\Api\TotalsInforma
      */
     public function calculate(
         $cartId,
-        \Magento\Checkout\Api\Data\TotalsInformationInterface $addressInformation
+        TotalsInformationInterface $addressInformation
     ) {
         /** @var \Magento\Quote\Model\Quote $quote */
         $quote = $this->cartRepository->get($cartId);
@@ -53,9 +53,19 @@ class TotalsInformationManagement implements \Magento\Checkout\Api\TotalsInforma
         } else {
             $quote->setShippingAddress($addressInformation->getAddress());
             if ($addressInformation->getShippingCarrierCode() && $addressInformation->getShippingMethodCode()) {
-                $quote->getShippingAddress()->setCollectShippingRates(true)->setShippingMethod(
-                    $addressInformation->getShippingCarrierCode().'_'.$addressInformation->getShippingMethodCode()
+                $shippingMethod = implode(
+                    '_',
+                    [$addressInformation->getShippingCarrierCode(), $addressInformation->getShippingMethodCode()]
                 );
+                $quoteShippingAddress = $quote->getShippingAddress();
+                if ($quoteShippingAddress->getShippingMethod() &&
+                    $quoteShippingAddress->getShippingMethod() !== $shippingMethod
+                ) {
+                    $quoteShippingAddress->setShippingAmount(0);
+                    $quoteShippingAddress->setBaseShippingAmount(0);
+                }
+                $quoteShippingAddress->setCollectShippingRates(true)
+                    ->setShippingMethod($shippingMethod);
             }
         }
         $quote->collectTotals();
diff --git a/vendor/magento/module-sales-rule/Helper/CartFixedDiscount.php b/vendor/magento/module-sales-rule/Helper/CartFixedDiscount.php
index b1fda3e7867..01f155a08d7 100644
--- a/vendor/magento/module-sales-rule/Helper/CartFixedDiscount.php
+++ b/vendor/magento/module-sales-rule/Helper/CartFixedDiscount.php
@@ -51,6 +51,8 @@ class CartFixedDiscount
     ): float {
         $shippingAmount = (float) $address->getShippingAmount();
         if ($shippingAmount == 0.0) {
+            $addressQty = $this->getAddressQty($address);
+            $address->setItemQty($addressQty);
             $address->setCollectShippingRates(true);
             $address->collectShippingRates();
             $shippingRates = $address->getAllShippingRates();
@@ -220,4 +222,35 @@ class CartFixedDiscount
         }
         return $availableDiscountAmount;
     }
+
+    /**
+     * Get address quantity.
+     *
+     * @param AddressInterface $address
+     * @return float
+     */
+    private function getAddressQty(AddressInterface $address): float
+    {
+        $addressQty = 0;
+        $items = array_filter(
+            $address->getAllItems(),
+            function ($item) {
+                return !$item->getProduct()->isVirtual() && !$item->getParentItem();
+            }
+        );
+        foreach ($items as $item) {
+            if ($item->getHasChildren() && $item->isShipSeparately()) {
+                foreach ($item->getChildren() as $child) {
+                    if ($child->getProduct()->isVirtual()) {
+                        continue;
+                    }
+                    $addressQty += $child->getTotalQty();
+                }
+            } else {
+                $addressQty += (float)$item->getQty();
+            }
+        }
+
+        return (float)$addressQty;
+    }
 }