Fix structure position

app/models/item.rb

@@ -46,15 +46,17 @@ class Item
 
   def shift_to(new_parent, position)
     position = position.to_i
-    unless self.parent_id.to_s.eql?(new_parent) && self.position == position
-      new_parent = Item.find(new_parent)
-      current_position_sibling = find_by_parent_and_position(new_parent, position)
-      if current_position_sibling
-        move_above(current_position_sibling)
-      elsif self.parent != new_parent
-        self.parent = new_parent
-        save
+    new_parent = Item.find(new_parent)
+    current_position_sibling = find_by_parent_and_position(new_parent, position)
+    if current_position_sibling
+      if self.position > current_position_sibling.position
+        self.move_above(current_position_sibling)
+      else
+        self.move_below(current_position_sibling)
       end
+    elsif self.parent != new_parent
+      self.parent = new_parent
+      save
     end
   end