Firmware: tomato-RT-AC66U_RT-AC6x--140-AIO-64K NVRAM wiped. I have printers and laptops connected via WiFi to the RT-AC66U. Printers use 2.4GHz. (Epson WF-4360) Laptops use 5GHz. (Lenovo 4xx with Intel® Dual Band Wireless-AC 7260) Everything works fine until left overnight, at which point it is not possible to ping/print/access the printers from the laptops. If the laptops are disconnected & reconnected to WiFi, access is again available for the day. Restarting the router resolves the issue. Changing the laptops to the 2.4GHz band resolves the issue, as does connecting either printer or laptop to the physical LAN, or using a print queue (W2K8 R2) on the physical lan. Restarting the laptop(s) or printer(s) does not usually resolve the issue, though explicit disconnection/reconnection of the WiFi does. But communication between devices on different bands is broken *after* being left overnight. To reiterate, everything works during the regular work day. It's only overnight that the ability to route from 5GHz devices to 2.4GHz devices is lost. I assume that several hours of inactivity at any time would create the same problem.