public class Profile{
  private String surname;
...
}

@ClassBridge(name = "customIndexingClassBridge", impl = CustomIndexingClassBridge.class)
public class DangerousEvent{

  @OneToMany(mappedBy = "compositeKey.dangerousEvent", fetch = FetchType.LAZY)
  Set<DangerousEventLinkedProfile> profils;
...
}

@ClassBridge(name = "customIndexingClassBridge", impl = CustomIndexingClassBridge.class)
public class DangerousEventLinkedProfile{
  @Embedded
  private DangerousEventLinkedProfileID compositeKey = new DangerousEventLinkedProfileID();

  private String tag;
  ...
}

@Embeddable
public class DangerousEventLinkedProfileID{

  @ContainedIn
  @ManyToOne
  DangerousEvent dangerousEvent,
 
  @ContainedIn
  @ManyToOne
  Profile profile;

...
}

..
@PersistenceContect
EntityManager em;

// DONT WORK
public void wontWork(){
  DangerousEvent dangerousEvent = new DangerousEvent();
  Profile profile = new Profile();
  profile.setSurname('test surname');

  DangerousEventLinkedProfile link =  new DangerousEventLinkedProfile();
  link.getCompositeKey().setDangerousEvent(dangerousEvent);
  link.getCompositeKey().setProfile(profile);

  em.persist(link);

// The index misses "surname" field;

}

// WORK WELL
public void workAndIndexCorrectly(){
  DangerousEventLinkedProfile link = em.find(DangerousEventLinkedProfile.class , existingUUID);
  link.tag = 'test';
  em.merge(link);

// Index fills "surname" field;

}