With hibernate cascading merge from Child to Parent leads to same child row inserted twice and Unique constraint violation

Environment

• Enterprise Application Platform < 5.0
• Hibernate < 3.3.2

• Domain Model like

  @Entity
  public class BarEty {
      @Id
      @SequenceGenerator(name = "seq", sequenceName = "Sq_Id_Bar")
      @GeneratedValue(generator = "seq")
      @Column(name = "Id_Bar")
      private Long id;
  
      @Column(nullable = false, unique = true)
      private String name;
  
      @ManyToOne(cascade = { PERSIST,  REFRESH, MERGE })
      @JoinColumn(name = "Id_Foo", nullable = false)
      private FooEty foo;
  ...
  
  @Entity
  public  class FooEty {
      @Id
      @SequenceGenerator(name = "seq",  sequenceName = "Sq_Id_Foo")
      @GeneratedValue(generator = "seq")
      @Column(name = "Id_Foo")
      private Long id;
  
      @OneToMany(cascade = CascadeType.ALL, mappedBy = "foo")
      private  List<BarEty> bars = new ArrayList<BarEty>();
  ...