In general everything works fine using Varnish enable w/ Turpentine extension. All of the standard areas of the admin section work as expected.
The issue comes when I navigate to an extension in the admin that does not use the standard /index.php/admin. Navigating to these extension I get logged out of the admin section.
We use a number of extensions that use these sort of urls. All have the same issue. It goes away when disabling Varnish or add the Varnish bypass cookie.
I have updated the URL Black list setting in Magento to reflect these urls. But the issue persists.
cron\.php helpdeskadmin mstcore pointofsale advancedinventory massstockupdate
The issue is also intermittent. Many times, after fiddling with the settings, these extensions are again accessible, but given a day or so, the issue returns.
Other relevant info:
Hosted at https://magemojo.com/ Using nginx php 5.6 fpm Magento 18.104.22.168 with all security updates