Welcome to the Community!
We were able to locate your account using your community details and learned that the router is already out of warranty.
Also, the router shows a stable connection from the NBN server.
For WiFi issues, signal interference may be causing the problem. We've created some articles that will help you improve it.
You have the option to use a third party router that is NBN compatible for the service. Since your service is NBN FTTP (Fibre to the Premises), you just need to configure a router to PPPoE with your TPG username and password.
Let us know if you need further assistance.