MAGETWO-91559: Static blocks with same ID appear in place of correct block

Author: mcahriman

app/code/Magento/Cms/Model/ResourceModel/Block.php

@@ -183,10 +183,12 @@ public function getIsUniqueBlockToStores(AbstractModel $object)
         $entityMetadata = $this->metadataPool->getMetadata(BlockInterface::class);
         $linkField = $entityMetadata->getLinkField();
 
-        if ($this->_storeManager->isSingleStoreMode()) {
-            $stores = [Store::DEFAULT_STORE_ID];
-        } else {
-            $stores = (array)$object->getData('store_id');
+        $stores = (array)$object->getData('store_id');
+        $isDefaultStore = $this->_storeManager->isSingleStoreMode()
+            || array_search(Store::DEFAULT_STORE_ID, $stores) !== false;
+
+        if(!$isDefaultStore) {
+            $stores[] = Store::DEFAULT_STORE_ID;
         }
 
         $select = $this->getConnection()->select()
@@ -196,8 +198,11 @@ public function getIsUniqueBlockToStores(AbstractModel $object)
                 'cb.' . $linkField . ' = cbs.' . $linkField,
                 []
             )
-            ->where('cb.identifier = ?', $object->getData('identifier'))
-            ->where('cbs.store_id IN (?)', $stores);
+            ->where('cb.identifier = ?  ', $object->getData('identifier'));
+
+        if(!$isDefaultStore) {
+            $select->where('cbs.store_id IN (?)', $stores);
+        }
 
         if ($object->getId()) {
             $select->where('cb.' . $entityMetadata->getIdentifierField() . ' <> ?', $object->getId());