Goofs

In the "heat tunnel" scene, Jack burns his arm when it touches the wall for a moment. However, as Archer opens the last door, Melanie puts her hand directly on the wall without even noticing.

All of the new zombies on the island were heat-treated to artificially age them, which had the added effect of making them slow-moving. In the final scene with the newscaster, there are zombies running in out of the surf.

The rifle Archer uses is a bolt action rifle, meaning the bolt should be opened and closed after each shot. However, it is used and fires like a semi-automatic rifle, firing consecutive shots without moving the bolt handle.

See-through magazines show no ammunition being spent, although characters fire more than magazines could hold.

The quote "The security in this place is water tight" makes no sense.

In the initial exposition, it's explained that the last major concentrations of undead (except for the Rezort island) were wiped out ten years in the past. However, nobody ever questions how it's possible that the Rezort has had undead shooting expeditions for years without ever running out of them.

When the Brimstone Protocol is activated, there is a several hours long delay before it is implemented, presumably to allow island staff a chance to escape. If the Protocol is intended with the priority of destroying the undead with no regard to human collateral damage (as mentioned in the opening exposition), then the attack should have been immediate.

The Brimstone protocol is activated due to the island's security being breached. This makes no sense because an attack on the facility's staff wouldn't result in the zombies getting off the island.

Majority of characters do not have any trigger discipline, not even seasoned veterans, employees or ex-military.