The orientation of the knife changes between Colonel Hart slamming it into the table and Captain Boyd using it.
While Captain Boyd was lying in the hole after falling from the cliff the phases of the moon were shown to illustrate the passing of time. It was clearly a waxing moon on the northern hemisphere (The "arc" was on the right side). But the moon was becoming thinner in time just like a waning moon.
When Boyd and Reich enter the cave, Colquhoun remains outside with hands tied. But, mysteriously, when the scene cuts back to Colquhoun his hands are free and he is gesturing madly. The next time the scene cuts back to Colquhoun he's holding a big knife in his hands; he could have dug up the knife from the dirt and used it to free his hands, although the rope is not on the ground by the hole (which he most likely threw away so as to not have it used on him again).
At one point when the soldiers are in search of the rest of Colquhoun's party, one of them kicks a patch of snow which folds over showing it to clearly be a piece of white cloth.
When Colqhoun is shot in the shoulder by Boyd it was clearly on his right. Later in the movie when The General asks him to prove that he was never shot he shows his right shoulder first and Boyd doesn't seem to care, but when Colqhoun shows his left shoulder with no wound he starts shaking in disbelief. How the crew overlooked this crucial detail is very surprising.
In 1848, Ives says "I reached Denver that spring ..." (of 1847), but Denver wasn't founded until 1858.
When Colqhoun is in the bath after being found outside, you can see a smallpox vaccination scar on his right shoulder.
When the men discover the cave there are a few tree stumps in that area that were sawed off flat. Since they are days away from civilization it would have been unlikely for someone to have come and harvested timber from that part of the wilderness.
While standing at the edge of the cliff, Colquhoun imitates a bomb being dropped out of an airplane by whistling (the sound they made while falling) and mimicking an explosion. Bombs were not dropped from balloons until the Austro-Italian war of 1849 (a year after the movie setting), and were not dropped from airplanes until the 1910s.
Around 0:52 Minutes in the Film , When Boyd escapes the hole and walks down the snowy hills crew members are clearly visible at the bottom.
Characters frequently make references to the Wendigo legend. This is very particular of the Algonquian tribe of northeast Canada, not California.
A single horse weighs over 1,000lbs, Colqhoun's group had several horses and several oxen. This would have been thousands of pounds of meat for 10 people for a few months at most.
Eating human bodies is practically a death sentence , not in any way shape or form medically beneficial.