Cache is not updating
By looking at the filecache module description:


  This module allows Drupal cache bins to be stored in files instead of
  storing in database.


This means that the data is stored in a folder and I guess this folder is not shared between your web servers.

I think you have 3 options:


(easy solution) Disable Filecache and rely on the builtin cache of drupal. This will store the bins content on your database and it will be shared/invalidated for your two servers as they share the same DB
(best solution) Replace FileCache with another caching module as Memcache or Redis. Depending on your server you might want to run those in a separate virtual machine and link them back to your web servers.
Share the folder used by FileCache across your servers.


Hope this helps.