Re: XR500 Lan Ports - Fatal Flaw
For a start disabling your firewall is not a great idea, those protections stop nasties getting through, and those packets may get dropped brieffly but will if needed make it as the router tends to be a biut paranoid but better than letting everything though as it is now. It will drop malformed packets, so when a packet with an error is received by the interface of the router, it will throw up a log entry and drop the packet. Running without a firewall is dangerous tbh.
Just a long shot but in settings Network setup, did you set connection mode to always on, and Idle time out time out to 0? If not the ports go to sleep till they are needed, which is dictated by the idle timeout. So over night with not much going on that may well happen. Just a thought.