Character mistake: When Curtin shoots Dobbs, the two shots are close together in time. When Curtin explains it he says that he was shot and falls. Then Dobbs shoots him again. This takes time but the shots were fired very quickly.
Other mistake: When the old man was resuscitating the unconscious boy he kept his arm sticking up in the air. His arm should have been besides his body, limp and unmoving.