Pixelated zig zag?

[(XBOX)Ancient Mutt]

Since the update, whenever I play/watch the opening cinematic for the beginner quest, I get a kind of blocky zig zag across the diagonal of my screen. It's more apparent when there's a very fast animation. It persists throughout the new surroundings of the quest too and is more apparent whenever I move quickly.

I don't get it during normal gameplay elsewhere though.

Is it me, my Xbox or a problem with the game or... ? 

Not sure if to report it as a bug because I can't seem to capture it correctly either. It's a shame because it makes the whole experience look like I just bought a pirate dvd.