nested forms dont show error messages

[sandbava]

Symfony version(s) affected: 5.0.9 (also in 5.1.0)

Description
Since my last composer install (3 June 2020), my nested forms (other form fields are ok) don't show error messages in html form anymore.
For example one field is instantiated like this in twig {{ form_row(form.birthplace.postal_code) }}.
If I put a wrong postal code in the html form, Symfony doesn't validate my form (correct behavior) but won't show error message corresponding to my constraints (incorrect behavior).

How to reproduce

PHP

nested form :

class BirthPlaceType extends AbstractType
{

    public function buildForm(FormBuilderInterface $builder, array $options)
    {
        $builder
            ->add('postal_code', TextType::class, [
                'label' => 'Postal code',
                'property_path' => 'birthplace.postalCode',
                'required' => true,
                'constraints' => [
                    new NotBlank(),
                    new Regex([
                        'pattern' => '/^(?:[0-8]\d|9[0-8])\d{3}$/',
                        'message' => 'validator.address.postal_code'
                    ])
                ]
            ])),
//[...]

host form :

class RegistrationType extends AbstractType
{
    public function buildForm(FormBuilderInterface $builder, array $options)
    {
        $builder->add('birthplace', BirthPlaceType::class, ['data_class' => UserProfile::class])
//[...]

controller :

class RegistrationController extends AbstractController
{
    public function form(Request $request)
    {
        $form = $this->createForm(RegistrationType::class, new UserProfile());
        $form->handleRequest($request);

        if ($form->isSubmitted() && $form->isValid()) {
            //[...]
        }

        return $this->render('registration/form.html.twig', ['form' => $form->createView()]);
    }
}

TWIG

form.html.twig

//[...]
{{ form_start(form) }}
{{ form_row(form.birthplace.postal_code) }}
//[...]
{{ form_end(form) }}
//[...]

[xabbuh]

Is this the same as #37025 and #37027?

[sandbava]

Different problem

[xabbuh]

Can you then please create a small example application that allows to reproduce your issue?

[sandbava]

githubdemo.zip

[xabbuh]

@sandbava Thank you for the example. However, this works for me when I apply the patch from #37085.

[sandbava]

I confirm, the patch do the work.
Will it be applied to version 5.1 ? Because I see it was for version 3.4.

[xabbuh]

Yes, we merge bugfixes in the lowest affected branch that is still maintained and from there merge it up to all other maintained branches.