Did you install the utility? Under advanced, you can select online game. Does it help? Besides, plug them into wall sockets directly to test. Confirm that you won't lost connection when xbox is...

Tried on a different PC? You should report this issue to the support staff directly.

W8970 V3 with guest network feature has been released...Hard to say if TP-LINK will still release any newer firmware for V1...

Cannot.

Reset the new one, TD-W8970 to factory defaults and reconfigure it. If it works normal, on its status page, check and write down upstream and downstream, or just save it as a screenshot. Compare it...

Augusto, it sounds faulty...Try to get it replaced under warranty.