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.
Factual error: Throughout the film, Lieutenant Choi and his platoon use a radio with a handset to communicate with their base. The radio however has an H-250 handset, which wasn't introduced until 1987, and the film takes place in 1972. The radio handset should be the H-189, which is the correct model for the Vietnam war from 1966 onwards.
Factual error: After Deni fires the last shot in her pistol, she continues to pull the trigger and the gun continues to click. However, this would not happen in a single-action semi-automatic like the Glock she is firing.