Unfortunately, you have not specified how the Bluewin TV box is connected to the data network. If it is connected via WLAN like the TV, then connect the TV box directly to the router with an Ethernet cable and see if it works better.
“Nothing has changed” is almost never the case with WLAN, your neighbours are already causing changes, such as overlapping channels or other interference in the network.
Lesen, was auf dem Bildschirm steht.