I think its that comics/cartoons don't really have a "world model" for the machine to build. Like, with photos, the lighting and physics and stuff all follow some rules and one could build a 3d model from a photo. But with comics/cartoons, everything is exaggerated, 3d models don't exist, lighting is vibes-based, every character is only drawn from certain angles. Let's say the machine determines it needs to draw the cartoon character in a 45 degree angle, but all the training data only had 0 and 60 degree angles. So it would try to base it on the 3d model it should have, but trying to make a 3d model of a cartoon character just results in contradictions. So it probably displays the contradictory result, which is then of course completely wrong.