During the initial meeting with Captain Talbot, Corporal Barnes is also referred to as Sergeant during the discussion.
In the 35th minute, Sgt. Armstrong cannot get his security card to work on the mechanical room door, and uses a push bar to open the door. Mechanical rooms always having a lock so or security card access that no one could affect the property's mechanical rooms (heat, cold, etc.). Therefore, the push bar would not open the door when his security card doesn't work.
For a payphone, one doe not need change or a credit card to call 911.
Velociraptors were much smaller in real life. They look more like Utahraptors.
Prison doors which are opened automatically cannot be closed manually.