ConstraintViolationException no Hibernate

Assuntos Gerais
#1

Olá pessoal, sou iniciante no uso do Hibernate e preciso de ajuda.

Problema:
O código abaixo funciona durante um tempo, após realizar 6 registros aproximadamente surge e o erro nada mais pode ser feito.

Exception:
ConstraintViolationException: Cannot add or update a child row: a foreign key constraint fails (gercom.frequencyregistration, CONSTRAINT FKC6FAE81593484615 FOREIGN KEY (idFrequencyRegistration) REFERENCES MemberLab (idMemberLab))

Codigo XHTML

<p:selectOneMenu value="#{frequencyregistration.idMemberLab}">
      <f:selectItems value="#{frequencyregistration.members}" var="member" itemValue="#{member.idMemberLab}" itemLabel="#{member.name}"/>
</p:selectOneMenu>
<p:selectBooleanButton value="#{frequencyregistration.register}" onLabel="Entrada" offLabel="Saída" onIcon="ui-icon-check" offIcon="ui-icon-close"/>
<p:commandButton value="ok" action="#{frequencyregistration.save}" ajax="false"/>

Codigo Java ManagedBean

public FrequencyRegistrationBean() {
        session = HibernateUtil.openSession();
        members = loadMembers();
        register = true;
        memberLab = new MemberLab();
        frequencyRegistration = new FrequencyRegistration();
    }
    
    public void save() {
        System.err.println("Initializing the save process");
        Transaction t = session.beginTransaction();
        for (MemberLab m : members) {
            if(m.getIdMemberLab().equals(idMemberLab)) {
                memberLab = m;
                break;
            }
        }
        frequencyRegistration = new FrequencyRegistration();
        frequencyRegistration.setMemberName(memberLab);
        frequencyRegistration.setDateRegistration(new Date(System.currentTimeMillis()));
        if(register)
            frequencyRegistration.setIngressHour(date);
        else
            frequencyRegistration.setExitHour(date);
        session.save(frequencyRegistration);
        t.commit();
        System.err.println("Finishing the save process");
    }
    
    private List<MemberLab> loadMembers() {
        Criteria criteria = session.createCriteria(MemberLab.class);
        List<MemberLab> l = criteria.add(Restrictions.eq("valid", true)).list();
        return l;
    }
#2