At the 30:00 minute mark Clu Gulager knocks on his Ex-wife's front door, there's no screen door between them. When she opens the door to let him in she has to unlock a screen door to let him in.
When Cindy's boyfriend takes away the check printer, he leaves the cover on the table, later when Jack returns home, the cover is gone.
At the end, shortly before Jack is shot, he fires his gun at Ed, but there is no sound coming from Jack's gun.