MC-19260: Coupon code removed during tax/shipping calculation on checkout

Author: rostyslav-hymon

app/code/Magento/SalesRule/Model/Validator.php

@@ -244,6 +244,8 @@ public function reset(Address $address)
     {
         $this->validatorUtility->resetRoundingDeltas();
         if ($this->_isFirstTimeResetRun) {
+            $address->setBaseSubtotalWithDiscount($address->getBaseSubtotal());
+            $address->setSubtotalWithDiscount($address->getSubtotal());
             $address->setAppliedRuleIds('');
             $address->getQuote()->setAppliedRuleIds('');
             $this->_isFirstTimeResetRun = false;