@nicots89 , Welcome to the community!
I see that you have connected the UPC TV Box via WIFI 5GHz Can you please try the following solutions?
1. If possible, connect your UPC TV Box via LAN cable directly from your modem without switches, routers or powerline adapters in between.
2. if you can’t connect via LAN, you should rename one of your WIFI’s For the 5GHz Wifi you can add a _5GHz at the end. Then you connect your UPC TV Box via 2.4GHz WIFI.
Greetings
Daniele