Drupal Webform not submitting sometimes right after clearing cache
Turns out that this issue was happening to me locally so it wasn't Memcache or Varnish that was causing this issue.  It turned out to be a webforms module. 

Because I was embedding the form on another node the '#action' value was incorrect.  I didn't run into this issue in the past because the code was updated on a newer version of webforms.

One fix is to use hook_form_alter() to change the action:

if ($form["#node"]-&gt;type == "stage_one_form" &amp;&amp; !path_is_admin(current_path())) {
  $alias = "/" . drupal_get_path_alias("node/{$form['#node']-&gt;nid}");
  $form['#action'] = $alias;
}


Another fix is to run the patch I created here.