At the end when he is shown hanging, the first shot shows him with his head tilted down and eyes closed. In the next shot, his face is tilted up and his eyes are open.
In the dialogue, a zombie incorrectly identifies himself as a vampire.
Towards the beginning, we see Pak exiting the elevator through a reflection of Chin's sunglasses. In this image, we also see the floor number 24. However, since this is being seen via reflection, the number 24 should be reversed as a mirror image, but it is not.