Why does my tv pixel on some channels

@williammckinlay do you stream, cable, satellite, or over the air. When you watch the BBC do you watch the other channels the same way or is it changing from let's say streaming to cable. If so, then the issue could be the main board. Try all the other video input sources. Also, you may want to check the cable, especially if you use HDMI for your TV. Some cables can cause this as well. You said that the TV is very new. Before doing anything else, contact Toshiba or the seller of theis TV and clarify any warranty on it. Don't fix what is their responsibility. Let us know what your screen shows buy posting some pictures of that with your Question. It might help us to narrow it down. iFixitでの質問に画像を追加する方法