Since the new interface, we experience in some case an unexpected session time out. This is cause by (in most cases) another tab/window that was not used for the timeout period, forcing all session (including your active one) to logout.

Of course this could be addressed, but maybe a more convenient solution (also for normal timeouts) might be to restore the session after you login again (within a certain time), or maybe even get a prompt if you want to continue where you left off.