about drupal8+commerce views filter display

i insert {{dump(items)}} to pager.html.twig to debug twig,then open product list page,turn page from first page to last page,some page can’t display pager . and the debug dump ‘items’ print ‘null’.why?

thanks very much.

Drupal version: 


Source: https://www.drupal.org/taxonomy/term/3/feed