only unsetting payment_method parameter when called in adminhtml orders.

Gateway/Http/Client/AbstractTransaction.php

@@ -22,6 +22,7 @@
 use Magento\Payment\Model\Method\Logger;
 use Psr\Log\LoggerInterface;
 use Stripe\StripeObject;
+use Magento\Framework\App\State;
 
 abstract class AbstractTransaction implements ClientInterface
 {
@@ -39,7 +40,10 @@ abstract class AbstractTransaction implements ClientInterface
      * @var StripeAdapterFactory
      */
     protected $adapterFactory;
-
+    /**
+     * @var State
+     */
+    protected $state;
     /**
      * AbstractTransaction constructor.
      * @param LoggerInterface $logger
@@ -49,11 +53,13 @@ abstract class AbstractTransaction implements ClientInterface
     public function __construct(
         LoggerInterface $logger,
         Logger $customLogger,
-        StripeAdapterFactory $adapterFactory
+        StripeAdapterFactory $adapterFactory,
+        State $state
     ) {
         $this->logger = $logger;
         $this->customLogger = $customLogger;
         $this->adapterFactory = $adapterFactory;
+        $this->state = $state;
     }
 
     /**

Gateway/Http/Client/TransactionSale.php

@@ -28,10 +28,23 @@ protected function process(array $data)
         $storeId = $data['store_id'] ? $data['store_id'] : null;
         // sending store id and other additional keys are restricted by Stripe API
         unset($data['store_id']);
-        unset($data['payment_method']);
         unset($data['shipping']);
-
+        // only unset payment_method param in backend.
+        if ($this->getArea() === 'adminhtml') {
+            unset($data['payment_method']);
+        }
         return $this->adapterFactory->create($storeId)
             ->sale($data);
     }
+
+    /**
+     * Get the current Area
+     *
+     * @return string
+     * @throws \Magento\Framework\Exception\LocalizedException
+     */
+    private function getArea()
+    {
+        return $this->state->getAreaCode();
+    }
 }