In recent years, the Internet has undergone many changes and many new rules and protocols have been created in order to work together with IP TV and streaming.
Spain is one of the countries that unfortunately has not been able to keep up with the development, you are simply still 20 years behind.

The infrastructure is of poor quality and the lines are overloaded, with all the new rules and protocols the traffic of data through Spain is too dense and data too difficult and difficult to get through, this especially goes beyond the TV signals.

If you want to understand how the internet and TV signals work together, you have to imagine 100 images, the TV box asks for 100 images (upload)
Server sends 100 images (Down Load), the TV box starts playing the first 100 images, when 80% have been played, the TV box asks for the next 100 images, they should ideally arrive at the TV box before the first 100 images have finished playing, if they do not arrive, the TV box stops and sets itself in a waiting position (black screen possibly with the buffer) until the box receives data again so that it can continue playing.