When the Predator spaceship destroys the U.S.S. Marlow in the Marine campaign, the shots are not as quickly fired as in the Predator campaign.
The Predator's thermal vision is inconsistent in its display of heat signatures. Dark-skinned characters appear to be cooler than light-skinned characters, and all humans appear warmer than fire.
When the Alien performs executions in front of other characters, sometimes they may say 'They took him apart' before the execution is even started.
The mission summary at the end of the final Predator level states that there are ten collectibles to be found when there are in fact only five.
The radio tower that the Alien must sabotage is short and surrounded on two sides by rock, which would render it useless for long range communication.