Form processing issue while generating a dynamic form and preparing via API calls directly
I fixed it this way, it started to invoke form submit handlers.

function MODULE_init() {
    if (!empty($_POST) &amp;&amp; $_POST['form_id'] == 'form_user_confirmation') {
        $form_state = form_state_defaults();
        $form_id = 'form_user_confirmation';
        drupal_build_form($form_id, $form_state);
    }
}