Continuity mistake: When Miguel opens the gate a herd of zombies come in. Later, when some zombies come from the bunker where they kept the specimens, several of the zombies are the same, and an obvious one is a kid in a football uniform. The zombies in the bunker had no way out, so how could the zombies be in two places at once?
Continuity mistake: At the climax of the film when the military guy shoots himself through the mouth to avoid being eaten alive, the closeup shot of him killing himself leaves a huge spatter against the wall he is in front of. In the next shot where he is falling to the ground, the fresh blood splatter is gone (or, at least, very less apparent).