I just picked up the XR500 after reading some reviews and from the recommendation of friends. This issue has plagued me daily since getting the router.
I keep getting a "Can't find Teredo IP Address" error for my Xbox One X (wired, Alpha updates). I have a Xbox One Day One (Wi-Fi, Alpha updates) in another part of the house and it doesn't get the same issue. It sometimes goes moderate on COD WII though. I also have a PS4 but haven't seen any issues except for it collecting dust.
I did set up Port Triggering rather than Forwarding. Could that be part of my issues? It looks like some other people are having similar difficulties but I can't make out where to start.
Please let me know if you need additional information. I'm somewhat of a networking noob but I usually figure things out.