sessions being read inconsistently
The site was on amazon AWS (without load balancing), so I set an appId in the config/general.php file to keep the session "sticky", even if the filepaths were "inconsistent" on a single server instance. The autogenerated appId based on filepath must have been interacting weird with Amazon's cloud setup.

return array(
    '*' =&gt; array(
    'appId' =&gt; 'myAppId',
),