Why is the screen pixelated in the top right corner?

70” Vizio. Smart TV.

There is an area, about 6” square, in the top right corner of the screen that is pixellated. The overall quality of the picture is not as clear as it should be, for being only a year old. We have adjusted the colour settings, brightness, tint, etc. and it hasn’t helped. When we changed it from vivid, though, it helped normalize it some, but not completely. Still pixellated. We receive programming via Dish Network and are connected to the internet. We don’t seem to have as severe a pixellation issue when watching YouTube or other video platforms as is present when watching Dish programming. Is it maybe missing an update?