To reproduce:
- Add bindingnavigator and data entry bound to a single binding source.
- Change one of the default editors to drop down list which is also bound to a datasource.
- Synchronize the selected value in the binding source CurrentChanged event.
- Press the move to the last item button.
- You will notice that the value is not displayed properly (displayed is the value member not the display member)

Workaround: 
void radBindingNavigator1MoveLastItem_Click(object sender, EventArgs e)
{
    bs.MovePrevious();
    bs.MoveNext();
}