After they've found the cabin, Charles offers to make tea. However, it's going to be some pretty lousy tea. We first see him dump a bunch of dirt out of the tea kettle. Next, we see him scoop some river water and offer to make some tea. He forgets to rinse the kettle out before heading inside to make his dirt tea.
After the flares have been lost, Bob says that he has only 6 matches left. In a later scene he is shown to have wasted a match to light a cigarette. He should have waited until they built a fire for heat or to attract searchers.
After Charles bandages Stephen's cut leg, he points up at the starry night sky. One minute later, Charles joins Bob along the lake edge, but at this point it is only dusk - there is clearly still light in the sky.
When Morse and green stop by the river, Green states that he is tired. Morse suggests baiting some fish with gold. As you see him construct his lure he is relatively clean shaved. In the next shot as he is lowering his lure he has at least a five day growth.
During the bear's attack on Stephen: Bob and Morse attempt to scare the bear off with torches lit from the campfire. However, there was a major downpour in the moments before and during the bear's attack. One wonders how the campfire, which can be seen burning well, would not have been extinguished by the rain.
Evading Bart, Charles is trying to cross log over the river. He drops his bag. The bag hits a branch, then the strap clearly comes apart and the bag falls. In the immediate next shot, the bag is back on branch.
Even if the paper clip had been properly magnetized using the knife, chances are exceedingly high that magnetic north would have been to the northeast or even east-northeast from their location, whose exact location was never given.
When discussing Kodiak bears, Styles says that they are highly aggressive, readily attacking and killing people without provocation. In fact, Kodiak bears are very shy, and when they encounter human beings, they typically withdraw. (Attacks do occur, but they are quite rare and almost never fatal.)
Charles says that, in the constellation Cassiopeia, one of the lines that form the distinctive "W" shape points toward Polaris, the North Star. It doesn't. (He may have been misremembering the Big Dipper, which does have two stars that point toward Polaris.)
In the plane Robert Green (Alec Baldwin) tells his passengers that his new watch is a GMT (dual time zone) watch. However at the end of the movie we see that the actual watch of Robert is an Omega Seamaster 300M Chrono Diver and this type of watch isn't a dual time watch.
When Bob and Charles reach the abandoned cabin, Bob finds a Winchester model 1886 rifle and 45-70 Gov't. cartridges and starts loading it. Although the cartridge caliber is correct for the rifle, the round nose bullets are not. .45-70 Gov't cartridges are rounded with a flat nose.
The fire that Charles and Bob make at 1:11 would theoretically work, and it'd sure be nice, but it wouldn't probably happen. The amount of dryfall that would be needed to sustain just ONE fire would be an ambitious endeavor. That part of the continent gets a lot of rain, therefore anything inland is liable to be wet. Areas on the riverbank may have some wood to get started. What a person would do is get something lit - anything - and they'd be smart to use the benefit of that heat to then help dry future wood (fuel). A person could then gradually move inland, but keeping any fire going in a damp climate is an enormous task. There's little chance in those conditions, at night, without huge stockpiles of fuel, that a person could keep up with it. Not because of lack of desire, just lack of practicality.
When Morse and Green fashion their bear-hide jackets there is some very neat stitching together of the pieces with straight seams in the back. This is not what you would expect in the wild. On top of that, it would take at least a week, using the necessary chemicals, to properly tan that bear's hide to make a suitable leather.