We are using Confluence with the F5 load balancing and quite often IE11 loses the session. When we inspect the call sequence IE11 is nicely sending the JSESSIONID cookie, but suddenly it doesn't send the JSESSIONID cookie and the server responses the error code 401 unauthorized.
When we don't use the F5 load balancing we are not able to reproduce the problem.
In the article https://connect.microsoft.com/IE/feedback/details/810700/subject-ie11-is-losing-cookie-information-and-thus-becoming-detached-from-a-web-application-session is a description about the session losing problem, but there is mentioned that the problem occurs when a new window is opened. This is not our case.
Normally we don't refresh the browser (use the F5 button), but if we press the F5 button, the problem occurs very fastly.