I've seen the problem before but it was a lot worse when I tried to watch a film (Churchill) on 10th August. Bad enough to make it unwatchable.
Every few minutes the picture starts breaking up or freezes. Eventually the sound stops too. Sometimes I could clear it by fast forwarding or rewinding a bit but it did the same again soon after. Sometimes the app freezes and the box reboots (3 times when trying to watch the film).
My broadband speed is fine (box is hardwired). Other apps work fine.
@huxley123 The only thing you can do with a third-party app is to raise a complaint with the app’s owner. In this case, Channel 5. If they get enough complaints, they might, just, be motivated to investigate and fix it.