Mauro1 Your plan does not work, not even with a modem reset. You are using WIFI extenders. These run via plume technology. This means that the WIFI networks have the same name for the 2.4/5GHz. The names cannot be separated, as this would make the MESH technology obsolete.
If you now want to separate the networks, you would have to remove the WIFI extenders and deactivate the WIFI optimization on the modem in the Admin interface. After a restart, you can then rename the WIFI networks.
Please note that your mobile devices will then have an interruption when they switch from 2.4 GHz WIFI to 5 GHz WIFI and vice versa.
Your TV Box is currently using channel 60 of the WIFI and the channel has a maximum utilization of 17%.

Greetings
Daniele