Found shared references to a collection: OneToMany empty collections refering to same PersistentBag

I've the following model : An Organization has a List<Contract>, each Contract may have a pricebookId and a collection of PricebookEntry. Multiple Contract entities can have the same pricebookId. The Collection<PricebookEntry> is the result of a @OneToMany association with the pricebookId as JoinColumn.

Here is the postulate: An organization has 2 contracts and both contracts have no pricebookId.

And here is my problem: During an Hibernate session where this particular Organization is involved, Hibernate throws this exception: org.hibernate.HibernateException: Found shared references to a collection: Contract.pricebookEntries.

Indeed, both contracts have their pricebookEntries set to the same PersistentBag (same reference).

How can I fix this ?

Thank you for your help!

@Entity
public class Organization implements Serializable {

  @Id
  private String id;

  @Fetch(FetchMode.SUBSELECT)
  @OneToMany(fetch = FetchType.EAGER, mappedBy = "organization")
  private final List<Contract> contracts = new ArrayList<>();

}


@Entity
public class Contract implements Serializable {

  @Id
  private String id;

  @Column(name = "pricebook_id")
  private String pricebookId;

  @JoinColumn(name = "organization_id", referencedColumnName = "id")
  @ManyToOne(fetch = FetchType.LAZY)
  private Organization organization;

  @JoinColumn(name="pricebookId", referencedColumnName = "pricebook_id")
  @OneToMany(fetch = FetchType.EAGER)
  @Fetch(FetchMode.SUBSELECT)
  private final Collection<PricebookEntry> pricebookEntries = new ArrayList<>();

}

@Entity
public class PricebookEntry {

  @Id
  private String id;

  private String pricebookId;

}