Yii2 ActiveForm Validation not working with bootstrap modal on first load

Question

"The ActiveForm validation will not work on the first modal load, BUT the second time, if you don't refresh the page and just close the modal window and load it again."

This happens on even the fresh install of yii2-app-basic.

What steps will reproduce the problem?

Create a view views/site/modal.php and add the modal code like below with an extra button and js code to open the modal window on button click and bind event shown.bs.modal to load the view inside the modal content section once modal is shown

<?php

use yii\bootstrap\Modal;
use yii\helpers\Html;

Modal::begin([
    'id' => 'contact',
]);
?>

<div class="modal-header">
    <h4>Contact</h4>
</div>

<div class="modal-body">

</div>

<div class="modal-footer">
    <?php
    echo Html::submitButton('Add Folder Now', ['class' => 'btn btn-primary']);
    ?>

</div>

<?php Modal::end() ;

 echo Html::button('button', ['class'=>'btn btn-primary','id'=>'add-folder-button']);

 $js=<<< js
        $("#add-folder-button").on('click',function(){
            $( '#contact' ).modal( {show:true});
            $( '#contact' ).appendTo("body");
        });

         $( '#contact' ).on( 'shown.bs.modal', function ( event ) {
            // var button = $(event.relatedTarget); // Button that triggered the modal
            let modal = $( this );
            modal.find( '.modal-header > h4' ).text( 'Contact Us' );
            modal.find( '.modal-body' ).load( 'contact');
        } );
js;
$this->registerJs($js,\yii\web\View::POS_READY);

Create an action inside the SiteController to load the above view

public function actionModal(){
    return $this->render('modal');
}

---

Now modify the actionContact inside the SiteController like below to be loaded inside the modal window

/**
     * Displays contact page.
     *
     * @return Response|string
     */
    public function actionContact()
    {
        $model = new ContactForm();
        if ($model->load(Yii::$app->request->post()) && $model->contact(Yii::$app->params['adminEmail'])) {
            Yii::$app->session->setFlash('contactFormSubmitted');
            return $this->refresh();
        }
        return $this->renderAjax('contact', [
            'model' => $model,
        ]);
    }

For the view, you can use the default contact.php view inside the views/site folder just add the below code on top of the view

$js=<<< js
        alert("hello");
js;
$this->registerJs($js);

What is the expected result?

on clicking the button the modal window should load and as soon the view is loaded it should show you the alert("hello"), and if I cycle/TAB through the fields it should run the ActiveForm client validation.

Note : i even tried providing 'enableClientValidation'=>true in the form options.

What do you get instead?

it Does nothing neither it shows the alert neither it runs the validation, instead if you close and then click the button again to open the modal window then everything works correctly. The alert is shown and the client validation works. but if you refresh the page again it won't work again until you open the modal window once and close it and open it again.

The above scenario works perfectly in Yii 1.x versions and I have it working I am working on a yii1.x extension to transform it into yii2.x

Additional info

| Q                | A
| ---------------- | ---
| Yii version      | 2.0.15.1
| PHP version      | 5.6
| Operating system | windows

Note: I added an issue on GITHUB-yiisoft but it was labeled as a question, although its the most basic setup to open a form inside a modal window and i have used it in the past but currently it isn't working, and this is not a normal behavior either it should work or it should not work at all if Yii does not support it.