The top right one is definitely not drawn by a human, it’s right out hexagons. Noone cross-hatches like that because you can’t cross-hatch like that there’s no lines going straight through.

The rest could be artistic choice, compression artifacts, or other stuff though. Well, some minor stuff, the topmost book on the left pile on the desk on the right is sus, and there’s way too many sponges at the base of the chalkboard. But none of them are dead tells like the hexagons.