NGUI table does not Reposition() properly

I have a table in a scrollview which I dynamicly fill from code. I iterate through an array of dataobjects, filling the data into a prefab-widget. All works so far. After the elements are all in the table I call the Reposition-method, but it is not properly executed. The paddinge between the elements in the table is much wider than I have set it. The only ways to properly Reposition() the tables elements I have found so far are a) right-clicking the table and chosing "execute" from the context-menu and b) adding Reposition() to the update-function having it execute every frame (sounds like a bad idea considering performance?)

What I tried so far: - putting Reposition() in Update() with a boolean/if-condition that makes it execute only once - trying the same as above with LateUpdate() I have not had any success so far. The Functions themselves seem to work, but they seem to have no effect on the table.

 for(int i = 0; i < _items.Length; i++)
 {
 
     var itemInstance = NGUITools.AddChild(ItemsPanel, ItemPrefab);
     var item = itemInstance.GetComponent<PrefabScript>();
     item.Icon.SetTexturePath = _items[i].IconPath;
     item.Level.text = _items[i].text;
     item.NotPresent.SetActive(_items[i].CurrentWeapon);
 }
 
 // make table sort itself
 // it doesn't work properly, no clue why
 ItemsPanel.GetComponent<UITable>().Reposition();