Input Attributes: "pattern" not working

I'm registering a field group for a CPT and can't have the pattern attribute working. No validation happens on the backend or frontend, Chrome or Firefox. I went back to the basics and created a new group with only one field following the example shown in the documentation and still does not work. Here's the code:

add_filter( 'rwmb_meta_boxes', 'nvf_register_mb_candidatura_form_input' );

function nvf_register_mb_candidatura_form_input( $meta_boxes ) {
    $prefix = '';

    $meta_boxes[] = [
        'title'      => __( 'Input Formulário dev', 'nvf-gb-front' ),
        'id'         => 'candidatura-form-details-dev',
        'post_types' => ['candidatura_bolsa'],
        'fields'     => [
            [
                'type' => 'text',
                'id'   => 'phone',
                'name' => 'Phone number',
                
                // Attributes for validation.
                'required' => true,       // Make the field required.
                'pattern'  => '[0-9]{9}', // Must have 9 digits
            ]
        ],
    ];

    return $meta_boxes;
}

Any ideas of what can be going on?

Thanks in advance.

EDIT: I'm using MB AIO Version 1.14.3 and MB Version 5.4.6