I've just deployed Meraki Wireless on on of our sites and I get a message in Event Details disassociated because device was idle for some iPads that I have for electronic visitor book.  I would think that you would get the same message if the device idled, unless there's a setting somewhere in the Meraki config for Idle timeout that I've not seen.   I know it's not the exact same issue that you are facing as it's not on a guest network, but just in case it helps. ... View more