By default, the ProxySG appliance attempts to pre-fetch (also known as Pipelining) content for URLs users request. In some cases, this happens before the website in question can perform additional tasks, (such as authentication or other user identification) the actual request may fail.
To avoid issues with Pipelining, you can create a Cache layer or Web Content layer rule to use the action Disable Pipelining. Steps for this are below.