Attempt to add columns or change settings in layout designer results in Page Not Found.

Using the "Builders" layout, whenever I try to change anything using the Layout Designer, I get a pop-up with the notification "Page Not Found."

Here's an export:

$handler = new stdClass();
$handler->disabled = FALSE; /* Edit this to true to make a default handler disabled initially */
$handler->api_version = 1;
$handler->name = 'page_technical_communications_syllabus_panel_context';
$handler->task = 'page';
$handler->subtask = 'technical_communications_syllabus';
$handler->handler = 'panel_context';
$handler->weight = 0;
$handler->conf = array(
  'title' => 'Panel',
  'no_blocks' => 0,
  'pipeline' => 'standard',
  'body_classes_to_remove' => '',
  'body_classes_to_add' => '',
  'css_id' => '',
  'css' => '',
  'contexts' => array(),
  'relationships' => array(),
);
$display = new panels_display();
$display->layout = 'flexible';
$display->layout_settings = array();
$display->panel_settings = array(
  'style_settings' => array(
    'default' => NULL,
    'top' => NULL,
    'left' => NULL,
    'right' => NULL,
    'bottom' => NULL,
  ),
);
$display->cache = array();
$display->title = '';
$display->content = array();
$display->panels = array();
  $pane = new stdClass();
  $pane->pid = 'new-1';
  $pane->panel = 'center';
  $pane->type = 'views_panes';
  $pane->subtype = 'technical_communications_syllabus-panel_pane_1';
  $pane->shown = TRUE;
  $pane->access = array();
  $pane->configuration = array();
  $pane->cache = array();
  $pane->style = array(
    'settings' => NULL,
  );
  $pane->css = array();
  $pane->extras = array();
  $pane->position = 0;
  $pane->locks = array();
  $display->content['new-1'] = $pane;
  $display->panels['center'][0] = 'new-1';
  $pane = new stdClass();
  $pane->pid = 'new-2';
  $pane->panel = 'center';
  $pane->type = 'views_panes';
  $pane->subtype = 'technical_communications_syllabus-panel_pane_2';
  $pane->shown = TRUE;
  $pane->access = array();
  $pane->configuration = array();
  $pane->cache = array();
  $pane->style = array(
    'settings' => NULL,
  );
  $pane->css = array();
  $pane->extras = array();
  $pane->position = 1;
  $pane->locks = array();
  $display->content['new-2'] = $pane;
  $display->panels['center'][1] = 'new-2';
$display->hide_title = PANELS_TITLE_FIXED;
$display->title_pane = 'new-1';
$handler->conf['display'] = $display;

I'm new to Drupal and web building in general, so please forgive me if this is a simple fix.

Another issue post addressed a similar problem, but it was very old and not for D7.