Continuity mistake: In the very beginning, just before impact, Walker goes out onto the balcony for a supposed security breach. Over the radio, the other officer refers to him as Sgt. Walker, but he, and others refer to him as Capt. Walker.
Factual error: Sarah is claimed to be "ex-SAS" - but the SAS don't have any women. Maybe they will one day, but Post Impact is set in the present day.