Remove duplicate records from views feed display for node with multiple grouped terms from one vocabulary
Here's what I came up with that does the job:

/**
 * Implements hook_views_query_pre_render().
 */
function video_export_views_pre_render(Drupal\views\ViewExecutable $view) {
  $unique_nids = $new_results = array();

  // Loop through results and filter out duplicate results.
  foreach($view-&gt;result as $index =&gt; $result) {
    if(!in_array($result-&gt;nid, $unique_nids)) {
      $unique_nids[] = $result-&gt;nid;
    }
    else {
      $new_results[] = $result;
    }
  }
  // Replace $view-&gt;result with new array. Apparently views requires sequentially keyed
  // array of results instead of skipping keys (e.g. 0, 2, 4, etc), so we can't just
  // unset the duplicates.
  $view-&gt;result = $new_results;
}