Listing pages with perch_pages_navigation() isn't showing pages

We're using the current location of the user to display a list of pages. In the directory we have a "subnav.php" file with the following:

<?php
function getNavPath() {
  $path_parts = explode('/', $_SERVER['REQUEST_URI']);
  $path_sections = array();
  foreach ($path_parts as $part) {
    if($part !== '' && strpos($part, '.php') === false) {
      $path_sections[] = $part;
    }
  }
  $path_sections = array_slice($path_sections, 0, 3);
  return '/'.implode('/', $path_sections).'/';
}

perch_pages_navigation(array(
  'hide-extensions' => true,
  'include-parent' => true,
  'levels' => 2,
  'from-path'=> getNavPath(),
  'template' => array('interior.html', 'basic-item.html')
));

?>

the code that displays the list is:

<perch:before>
  <ul>
</perch:before>
    <li><a href="<perch:pages id="pagePath" />" ><perch:pages id="pageNavText" /></a></li>
<perch:after>
  </ul>
</perch:after>

This works in one directory perfectly fine but when placed in another directory (with the same number of levels) it doesn't work. for example:

"mysite.com/library/books" - works "mysite.com/library/magazines" - doesn't work

It's acting like no pages exist in the directory when literally the same pages were copied into the directory (they all used shared regions).