Sequence of events that leads to this issue
1. User attempting an HTTP POST at an LB / CS resource with authentication enabled  [AAA Vserver, Form Based]
2. AAA session for the user was timed-out / expired on Netscaler.
3. User is redirected to AAA login page (as previous session has expired), authentication succeeds.
4. User is redirected back to original request path, but is presented with Http/1.1 Internal Server Error 43550 
5. At this stage no matter how many times you refresh the error won't go away. 
6. If the browser is closed and restarted able to access the resource again

Note - This could affect any resource behind LB / CS Vserver with auth enabled including but not limited to OWA

• ​This is a known issue with build 11.1.56.19
• The is resolved in 11.1.58.x (Tentative Release, April 2018)
• 12.0.x is not affected by this issue

Problem Cause