Plot hole: The whole plot of the first "Brother Bear" was that Kenai had to go to that mountain to become human. But at the end of this movie, the spirits were about to change Kenai back into a human in the middle of a cliff, which makes the entire first movie completely pointless.
Continuity: When Kenai is talking to Nita after she has turned into a bear, we can see that there is no one behind Kenai. When we cut to a wide shot, Koda is standing behind him.
Audio problem: Everybody knows that waterfalls are very loud. However, in the scene at Hakoni Falls, which is completely surrounded by waterfalls, it's silent as a tomb.
Plot hole: During the "Feels Like Home" montage, we see Nita jumping over the ground using a wooden pole. Where did she get it? There's no room on her person to carry it and it's never mentioned again.