Showing AnsPress Input Field instead title!

Hello,
I change the title length by using this code:

function my_custom_title_field( $form )
{
 $form['fields']['post_title'] = array(
  'max_length' => 600,
 );
return $form;
}
add_filter( 'ap_question_form_fields', 'my_custom_title_field' );

But now the title is changed to ‘AnsPress Input Field.’