Spring Data Rest merges data when updating relationships

Question

I am using Spring Data REST in my project and I have a problem with relationships when I edit the main entity. This is a simple version of my model:

@MappedSuperclass
public abstract class AbstractEntity {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;

    // Getters and setters
}

@Entity
public class Player extends AbstractEntity {

    private String category;

    private String fnuCode;

    @OneToMany(cascade = CascadeType.ALL, orphanRemoval = true)
    @JoinTable(name = "player_contact", joinColumns = @JoinColumn(name = "id_player"), inverseJoinColumns = @JoinColumn(name = "id_contact"))
    private List<Contact> contacts;

    @ManyToOne(cascade = CascadeType.ALL)
    @JoinColumn(name = "id_person")
    private Person person;

    // Getters and setters
}

@Entity
public class Contact extends AbstractEntity {

    @ManyToOne(cascade = CascadeType.ALL)
    @JoinColumn(name = "id_person")
    private Person person;

    private String relationship;

    // Getters and setters
}

@Entity
public class Person extends AbstractEntity {

    private String name;

    private String lastname;

    private String idCard;

    // Getters and setters
}

Then, I have my PlayerRepository:

@RepositoryRestResource(path = "players", excerptProjection = PlayerList.class)
@CrossOrigin(origins = "http://localhost:8081")
public interface PlayerRepository extends PagingAndSortingRepository<Player, Long> {

}

PlayerDetail is the projection I use when see and edit a player:

@Projection(name = "playerdetail", types = { Player.class })
public interface PlayerDetail {

    @Value("#{target.person.name} #{target.person.lastname}")
    String getFullName();

    @Value("#{target.person.idCard}")
    String getIdCard();

    @Value("#{target.category}")
    String getCategory();

    @Value("#{target.fnuCode}")
    String getFnuCode();

    List<Contact> getContacts();
}

I don't have any repository for contacts since they are created and modified into the player context.

This is a sample json response I get when I want to edit or see the details of a player (the object is generated from playerdetail projection):

{
 "idCard" : "12365478",
 "fnuCode" : "1111",
  "contacts" : [ {
    "person" : {
      "name" : "Roberto",
      "lastname" : "Perez",
      "idCard" : null
    },
    "relationship" : "Father"
  }, {
    "person" : {
      "name" : "Lucia",
      "lastname" : "Perez",
      "idCard" : null
    },
    "relationship" : "Sister"
  } ],
  "fullName" : "Juancito Perez",
  "category" : "U19",
  "_links" : {
    "self" : {
      "href" : "http://localhost:8080/players/171"
    },
    "jugador" : {
      "href" : "http://localhost:8080/players/171{?projection}",
      "templated" : true
    }
  }
}

The problem occurs when I edit the player and remove the first contact of the list, in this case, "Roberto Perez". As a result, in the database the row of Lucia Perez is removed and its data is merged in Roberto Perez row. Before deleting the first contact, I have the following data in DB:

Table: contact
id  |id_person  |relationship   |
175 |176        |Father         |  --> First contact (Roberto)
178 |179        |Sister         |  --> Second contact (Lucia)

Table: person
id  |id_card    |lastname   |name
176 |null       |Perez      |Roberto
179 |null       |Perez      |Lucia

After deleting first contact (Roberto), I have this:

Table: contact
id  |id_person  |relationship
175 |176        |Sister

Table: person
id  |id_card    |lastname   |name
176 |null       |Perez      |Lucia

Note that the ID for the second contact has changed. It should be 178 instead of 175.

EXPECTED RESULT:

Table: contact
id  |id_person  |relationship
178 |179        |Sister 

Table: person
id  |id_card    |lastname   |name
179 |null       |Perez      |Lucia

The second contact should keep its ID.

I suppose Spring Data REST merges contacts information because there is no univocal way to identify every contact since the id is not exposed in the projection.

I need a way of prevent contacts merging. Is there any other way of managing collections and relationships in Spring Data REST?