Continuity mistake: Ben Bart passed away earlier in the film but can be seen dancing on stage with the character Gertrude, at a James Brown concert where he is performing "I Got Soul (Super Bad) ". (01:46:00)
Suggested correction: During that sequence, they intercut James in his gold jumpsuit, with long hanging-down hair, and James in a black-and-white checked vest, doing the same song. In the black-and-white vest era, Ben Bart is still alive, so the dancing could have been from that era.
While that does seem to be the case, it should be pointed out that Ben Bart died in 1968, but the song James Brown is singing, "Super Bad", was recorded in 1970.
Factual error: When James' men are taking money to the bank, modern TV traffic cameras are visible at the intersection.
Factual error: In one scene that took place in the 1940s, the filmmakers used dollar bills like the current Federal Reserve Notes, which weren't in circulation back then. (They began circulating in 1964). They should have used Silver Certificates instead.
Factual error: In the scene where James Brown receives a new Cadillac from his manager, the scene is marked by a 1965 timeline header, but the Cadillac is actually a 1967 model.