Issue #3177590 by alexpott, longwave, hussainweb: ViewsFormBase::getForm()...

  public function getForm(ViewEntityInterface $view, $display_id, $js) {

    $form_state = $this->getFormState($view, $display_id, $js);

    $view = $form_state->get('view');

    $key = $form_state->get('form_key');

    $form_key = $form_state->get('form_key');

    // @todo Remove the need for this.

    \Drupal::moduleHandler()->loadInclude('views_ui', 'inc', 'admin');

    // it off; if it isn't, the user clicked somewhere else and the stack is

    // now irrelevant.

    if (!empty($view->stack)) {

      $identifier = implode('-', array_filter([$key, $view->id(), $display_id, $form_state->get('type'), $form_state->get('id')]));

      $identifier = implode('-', array_filter([$form_key, $view->id(), $display_id, $form_state->get('type'), $form_state->get('id')]));

      // Retrieve the first form from the stack without changing the integer keys,

      // as they're being used for the "2 of 3" progress indicator.

      reset($view->stack);

      $key = key($view->stack);

      $stack_key = key($view->stack);

      $top = current($view->stack);

      next($view->stack);

      unset($view->stack[$key]);

      unset($view->stack[$stack_key]);

      if (array_shift($top) != $identifier) {

        $view->stack = [];

    // Automatically remove the form cache if it is set and the key does

    // not match. This way navigating away from the form without hitting

    // update will work.

    if (isset($view->form_cache) && $view->form_cache['key'] != $key) {

    if (isset($view->form_cache) && $view->form_cache['key'] !== $form_key) {

      unset($view->form_cache);

    }