hook_panels_pre_render to create a new pane

I've used the hook_panels_pre_render to create a new pane that is added on every node of a specific type. ( movie in this case )

/**
 * Implements hook_panels_pre_render().
 */
function MYMODULE_panels_pre_render($panels_display, $renderer) {
  global $language;

  if ($node = $panels_display->context['panelizer']->data) {
    if ($node->type == 'movie') {
      $fpid = 1699;
      if ($language->language == 'en') {
        $fpid = 1721;
      }
      foreach ($panels_display->content as $panel) {
        if ($panel->subtype == "fpid:$fpid" && $panel->panel == 'row2_right') {
          return;
        }
      }
      $new_pane = panels_new_pane('fieldable_panels_pane', "fpid:$fpid", TRUE);
      $new_pane->panel = 'row2_right';
      $panels_display->panels['row2_right'][] = $new_pane->pid;
      $panels_display->content[$new_pane->pid] = $new_pane;
    }
  }
}

In the previous installed version (3.5) this added a new pane which I could edit.
Now I get a ajax error "Invalid pane id."
I've used the debugger to trace it to the edit link where the $pid = 'new' instead of an id.

Do I need to change this function to create a pane to insert in the region 'row2_right' ?