When Albert Johnson jumps into the pine tree he drops his rifle in the snow at the top of the cliff and it can be seen there after he jumps. When he falls to the ground the rifle is laying beside his pack. It is not the 2nd rifle that he had in his pack as that one is still visible in the pack.
When Johnson is trapped on the cliff and begins preparing to jump into the pine trees, the weather is sunny and there is no snow on the trees. Yet when he jumps, the sky is overcast and the trees are covered with snow; once he is back on the ground, it is sunny again and the snow is gone from the trees.
When the plane is shot, it's sunny. When it crashes a few seconds later, it's much cloudier and darker, like late afternoon. After the crash, it's all sunny again.
When Sundog is shot by the pilot in the biplane he is shown lying in the snow with his left arm across his face. When Millen kneels beside him he removes Sundog's right arm from across his face.
When Edgar Millen is talking to Albert Johnson in front of his cabin, although the background is blurry, you can still see that there's heavy rain. But there's no rain when he's walking to and away from the cabin, or for the rest of the scene.
When Bill is shot and killed by Millen he screams Aah! and falls down in the snow. Alvin is then asked to check out but he can't recognize Johnston because his face is blown apart. Thee are two mistakes here: a rifle shot does not blow a face apart and when your face is blown apart you are not able to scream as Bill did.
Alvin Adams transmits the call sign W6MQ over his radio. This is an amateur radio call sign issued by the United States, not an RCMP call sign issued by Canada.
When the posse member puts his arm in the bear trap and it is bleeding you can see the blade bend when he pulls his arm out, because the blades are made of rubber.
When Millen takes his revolver out of the suitcase he opens it and you can see that it is loaded. Then he closes it and without cocking it he sights along the gun. You then hear the sound of a cocked gun being dry fired, even though the gun was not cocked and was loaded.
When Johnson rolls down the hill after the airplane first catches up with him, there are already identical tracks visible on the hill side, presumably from the previous take.
What looks to be earplugs can be seen in Hazel's ear as he shoots at Albert Johnson's cabin.
When a guy gets his arm stuck in a bear trap, it is painfully obvious that the serrated teeth of the bear trap is made from rubber, as it bends unnaturally and moves about as the actor moves his arm.
The Alsatian (German Shepherd) dogs used to track Johnson early on in the film clearly have their barking sounds dubbed-over by Huskies or similar sled dog breeds which have a more distinct identifying bark or howl. Sled-pulling Huskies do appear later on in the film, however.
The machine gun mounted at the top of the plane is in alignment with the propeller. If it really had fired, it would destroy the propeller and cause a crash.
In the last aerial scene of the movie as Albert Johnsons is walking toward the camera and the camera is moving in reverse, ripples can be seen on the large puddle of water made by wind from the helicopter blades.
While Albert Johnson is making his escape through the forest, a modern highway guardrail appears clearly in the background. These guardrails were not in use during the time of this story, and Johnson was supposed to be out in the wilderness.
As Johnson jumps down from the cut tree, the safety cable attached to his back is visible.
Crickets can be heard chirping in the background during the quieter scenes at the Aklavik RCMP HQ on New Year's Eve 1932. In Canada's NWT at the Arctic Circle the average temperature outside on December 31st would be about -40c and any crickets dormant until spring.
Lee Marvin introduces himself at the cabin as Edgar Millen of the Royal Canadian Police instead of the Royal Canadian Mounted Police.