diff --git a/application/Api/v1/PreorderApicontroller.php b/application/Api/v1/PreorderApicontroller.php
index d97442974..0e586c191 100644
--- a/application/Api/v1/PreorderApicontroller.php
+++ b/application/Api/v1/PreorderApicontroller.php
@@ -505,8 +505,9 @@ class PreorderApicontroller extends mfBaseApicontroller {
       if(count($unit_search)) {
         $update_unit = true;
       }
-      
+
     } elseif($unit_search_count_without_stock > 0) {
+      
       //var_dump($unit_search);exit;
       if(array_key_exists("unit_string", $unit_search)) {
         $where .= " AND bezeichner LIKE '".$unit_search['unit_string']."'";
@@ -529,7 +530,9 @@ class PreorderApicontroller extends mfBaseApicontroller {
       } else {
         $update_unit = true;
       }
+
     } else {
+
       // if all unit values are empty try to find the unit with all empty values
       // failure is not an error, but must be checked by a human at some point
       $where = "hausnummer_id=".$address->hausnummer_id." AND (block = '' OR block IS NULL) AND (stiege = '' OR stiege IS NULL) AND (stock = '' OR stock IS NULL) AND (tuer = '' OR tuer IS NULL) AND (bezeichner = '' OR bezeichner IS NULL)";
@@ -546,26 +549,44 @@ class PreorderApicontroller extends mfBaseApicontroller {
       $sql = "SELECT * FROM view_wohneinheit WHERE $where";
       $this->log->debug($sql);
       $res = $this->db()->query($sql);
-      if($this->db()->num_rows($res)) {
-        $unit = $this->db()->fetch_object($res);
+      
+      $found_units_count = $this->db()->num_rows($res);
+      if($found_units_count) {
+        // check if unit has active preorder already and try next unit
+        $existing_preorder = false;
+        while($unit = $this->db()->fetch_object($res)) {
+          // check if there is an existing preorder
+          $existing_preorder = PreorderModel::getFirst(['adb_wohneinheit_id' => $unit->wohneinheit_id, 'deleted' => 0]);
+          if(!$existing_preorder) {
+            break;
+          }
+        }
+        if($existing_preorder && $this->exist_is_error && !$is_additional_order) {
+          return mfResponse::Forbidden(['message' => "Für diese Wohneinheit liegt bereits eine Bestellung vor"]);
+        }
       } else {
         // XXX - If there are no units without unit data maybe try finding a fitting unit without an order
         //$assign_unit = true;
       }
     }
     
-    if($this->exist_is_error && !$is_additional_order) {
-      /*
-       * check if there is an existing preorder for this unit already
-       */
-      if($unit && $unit->wohneinheit_id) {
-        $existing_preorder = PreorderModel::getFirst(['adb_wohneinheit_id' => $unit->wohneinheit_id, 'deleted' => 0]);
-        if($existing_preorder) {
+    
+    /*
+     * check if there is an existing preorder for this unit already
+     */
+      
+    if($unit && $unit->wohneinheit_id) {
+      $existing_preorder = PreorderModel::getFirst(['adb_wohneinheit_id' => $unit->wohneinheit_id, 'deleted' => 0]);
+      if($existing_preorder) {
+        if($this->exist_is_error && !$is_additional_order) {
           return mfResponse::Forbidden(['message' => "Für diese Wohneinheit liegt bereits eine Bestellung vor"]);
         }
       }
     }
     
+      
+    
+    
     
     $address_info = $this->db()->escape(trim($this->post['address_info']));