On IIS 8.5 we have an web application running with application pool's identity set to ApplicationPoolIdentity.
When we switch to Custom account instead of the ApplicationPoolIdentity then web application's user session is lost at random and also on app pool recycles.
But everything is ok with the ApplicationPoolIdentity.
We need to set the application pool's identity to Custom account for various reasons.
Any idea what is the issue with Custom account which is using a windows user account that has IIS_IUSRS permission.