Your modem has the latest firmware.
If you're only experiencing the disconnection on your LG Smart TV and other Wi-Fi devices are properly working, that only means that there's nothing wrong with your TPG service.
The issue could be on the LG Smart TV network settings or its compatibility with the new modem.
We have created these community articles, which may help you better understand the wireless connectivity and how the performance can be improved:
If you will encounter the same issue, we'd recommend that you contact LG for further assistance.