New entity found through relationship

1. I have a project in Symfony.

2. I create a form for a new entity.

   class EquipoType extends AbstractType{
   /**
    * {@inheritdoc}
    */
    public function buildForm(FormBuilderInterface $builder, array $options)
    {
       $equipo = new Equipo();
   
       $builder
       ->add('unidades', IntegerType::class)
       ->add('accionComercial', EntityType::class, array(
           'class' => 'AppBundle\Entity\IndicoGpt\adelantoequipos\AccionComercial',
           'em' => 'adeq',
           'choices' => $equipo->getAccionComercial(),
           'choice_label' => 'nombre',
           'placeholder' => 'Elija Accion Comercial'
       ))
       ->add('modelo', TextType::class)
       ->add('save', SubmitType::class, array(
               'label' => 'Guardar Equipo',
               'attr' => array(
                   'class' => "btn btn-info",
                   'style' => "margin-top: 7px; margin-left:40%;"
               ))
       );
   
       $builder->get('modelo')
           ->addModelTransformer(new CallbackTransformer(
               function ($modelo) {
                   return $modelo ? $modelo->getModDescModelo() :  $modelo;
               },
               function ($modelo) use ($options) {
                   return $modelo ? $options['em']->getRepository(ModModelo::class)->findOneBy(array(
                       'modDescModelo' => $modelo
                   )) : $modelo;
               }
           ));
    public function configureOptions(OptionsResolver $resolver)
    {
       $resolver->setDefaults(array(
           'data_class' => 'AppBundle\Entity\IndicoGpt\adelantoequipos\Equipo',
           'em' => "adeq"
       ));
    }
   
    /**
     * {@inheritdoc}
     */
    public function getBlockPrefix()
    {
       return 'appbundle_indicogpt_adelantoequipos_equipo';
    }
   }
   

3. This entity has a relationship. (A Team has a model, a model can be of many Teams)

   class Equipo
   {
       /**
    * @var \AppBundle\Entity\IndicoGpt\catalogo\ModModelo
    *
    * @ORM\ManyToOne(targetEntity="AppBundle\Entity\IndicoGpt\catalogo\ModModelo")
    * @ORM\JoinColumns({
    *   @ORM\JoinColumn(name="modelo_id", referencedColumnName="MOD_ID_MODELO")
    * })
    */
   private $modelo;
   

4. The models are already in the DB, that is. That a team should only save the existing id of a Model. Controller:

   public function crearEquipo(Request $request){
   
   $emAdeq = $this->getDoctrine()->getManager('adeq');
   $emCatalogo = $this->getDoctrine()->getManager('catalogo');
   
   $equipo = new Equipo();
   $form = $this->createForm(EquipoType::class, $equipo, array(
       'action' => "crearEquipo",
       'em' =>  $emCatalogo,
       'attr' => array(
           'class' => "form"
       )
   ));
   
   $form->handleRequest($request);
   
   if ($form->isSubmitted()) {
   
       $equipo = $form->getData();
   
       $emAdeq->persist($equipo);
   
       $emAdeq->flush();
   
       $this->addFlash('exito', $equipo->getId());
   
       return $this->redirectToRoute('portadaAdelantoEquipos');
   }
   
   
   return $this->render('AppBundle:AdelantoEquipos/forms:adelantosForm.html.twig', array(
       'form' => $form->createView()
   ));
   

   }

5. When I go to Save the new Team, it tells me that it has found a new entity in the relationship, but that entity is not new, it is an existing model that is now related to the Team. As can be seen in the image, I choose a model from the existing ones through an autocomplete field.

Just before doing the Persist of the entity, I can see in the debugger the object that I am going to record and it appears well composed:

The error is the following:

A new entity was found through the relationship 'AppBundle\Entity\IndicoGpt\adelantoequipos\Equipo#model' that was not configured to cascade persist operations for entity: AppBundle\Entity\IndicoGpt\catalogo\ModModelo@0000000011088ca600000000661c7dca. To solve this issue: Either explicitly call EntityManager#persist() on this unknown entity or configure cascade persist this association in the mapping for example @ManyToOne(..,cascade={"persist"}). If you cannot find out which entity causes the problem implement 'AppBundle\Entity\IndicoGpt\catalogo\ModModelo#__toString()' to get a clue.

I don't understand why it has a numeric code @0000000012ce55020000000059452bb5 or why it thinks it is a new entity.

Does anyone know what behavior Doctrine is having?

How can I record the Team entity with its relationship?

I have seen similar problems solved by resetting the objects by extracting them from the database, but that involves setting too many relationships. Here