difference between logged in users in CoovaAAA and CoovaAP

There is a difference between the logged in users displayed on the router under "HotSpot Status" and the active Sessions under "https://www.coova.net/aaa". After some time users get log-in problems and the only way to solve that is to restart the router.

Is there any fix or any idea how I can solve that problem.

Thank you for you support.