When Maury's character leaves the hut the cross bar on the door remains upright. When the woman escapes the pit, the cross bar is back in place.
When Hal finds Dr. Jordan's body, her eyes are open. In the next shot her are closed.
Although the iconic movie poster gives the title as DEF-CON 4, it actually appears in the film's credits as DEFCON-4.
The coordinates for the uncontaminated survival station, 62.17.20N 19.02.40E, are actually in the Gulf Of Bothnia between Sweden and Finland and there is no land mass there.
The shadow of the boom mic is visible on the space capsule just before 'blue jacket' is shot.