Entity with multiple reference to a composite-id foreign key throws EntityExistsException

Company.java

@Entity
public class Company {
  
  @Id
  public Long id;
  
}

Customer.java

@Entity
@IdClass(Customer.class)
public class Customer {
  
  @Id
  public Long id;
  
  @Id
  @ManyToOne
  public Company company;
  
  public Customer related;
  
}

CustomerId.java

public class CustomerId {
  
  public Long id;
  
  public Long company;
  
  @Override
  public int hashCode() {
    return (int) (this.id + this.company);
  }
  
  @Override
  public boolean equals(Object object) {
    if (object instanceof CustomerId) {
      CustomerId customerId = (CustomerId) object;
      return (this.id == customerId.id) && (this.company == customerId.company);
    } else {
      return false;
    }
  }
  
}

CustomerService.java

@Stateless
public class CustomerService {
  
  @PersistenceContext
  private EntityManager em;
  
  public void createCustomer() {
    Company company = new Company();
    company.id = 1;
    
    Customer customerOne = new Customer();
    customerOne.id = 1;
    customerOne.company = company;
    
    Customer customerTwo = new Customer();
    customerTwo.id = 2;
    customerTwo.company = company;
    customerTwo.related = customerOne;
    
    this.em.merge(customerTwo);
  }
  
}