Fixed stock status to "Out of Stock" after product import even product allowed backorders. .../module-catalog-import-export/Model/Import/Product.php

MagentoCatalogImportExport_Model_Import_Product.php.diff

--- /vendor/magento/module-catalog-import-export/Model/Import/Product.php
+++ /vendor/magento/module-catalog-import-export/Model/Import/Product.php (Unsaved)
@@ -3062,7 +3062,9 @@
         $stockItemDo = $this->stockRegistry->getStockItem($row['product_id'], $row['website_id']);
         $existStockData = $stockItemDo->getData();
 
-        if (isset($rowData['qty']) && $rowData['qty'] == 0 && !isset($rowData['is_in_stock'])) {
+        if (isset($rowData['qty']) && $rowData['qty'] == 0 && !isset($rowData['is_in_stock'])
+            && empty($existStockData['backorders']) // backorders not set or set to 0
+        ) {
             $rowData['is_in_stock'] = 0;
         }
 
@@ -3074,7 +3076,9 @@
         );
 
         if ($this->stockConfiguration->isQty($this->skuProcessor->getNewSku($sku)['type_id'])) {
-            if (isset($rowData['qty']) && $rowData['qty'] == 0) {
+            if (isset($rowData['qty']) && $rowData['qty'] == 0
+                && empty($existStockData['backorders']) // backorders not set or set to 0
+            ) {
                 $row['is_in_stock'] = 0;
             }
             $stockItemDo->setData($row);