Factual error: Near the end of the song "One Of Us" when Kovu is exiled, the beisa oryx at the front of the animal chorus (the one shaking her head slowly) has incorrect facial markings for her species. The other beisa oryx in the background has the correct markings. When she sings "He is not one of us," solo, she has correct facial markings, but lacks the correct leg markings, which she had when her facial markings were incorrect.
Factual error: Okapis attend events such as Kiara's presentation and Kovu's exile, despite the fact that okapis are native to the Congo rainforest, not the savanna. They would not be in the Pride Lands, and therefore should not attend these events.
Answer: It's since been revealed that Zira completely made up the bit about Scar choosing Kovu as his successor. Any errors or plot holes can thus be chalked up to that.