During the fight at the river between Cass and Jim, Cass's ankle bandage and socks variously disappear and re-appear.
During both encounters with Satan the grizzly, the closeups of its head and face were obviously of a fake bear that looked nothing at all like the real live shots of the bear.
When being warned about the Grizzly, "Old Satan", Big Jim responds that "a Winchester .44-40 ought to take care of him." The .44-40 is a large bore pistol cartridge still popular today for which the Winchester Model 1892 lever action rifle was chambered (the same rifle used by The Rifleman (1958)), but it is far too light to be reliable against an animal the size of a Grizzly. No hunter would ever voluntarily confront such an animal with a .44-40.
At one point the characters sing a variation of "Old MacDonald". The film appears to be set in the 1870s or 1880s. Old McDonald wasn't written until 1917.
When Big Jim steps in the bear track, his boot print leaves the design of a rubber sole. Leather boot soles are completely smooth.