Factual error: Near the end of the movie, a DJ announces over the air that the crash had occurred that killed Buddy Holly, J.P. Richardson (commonly known as "The Big Bopper"), and Ritchie Valens. The DJ then plays the Santo & Johnny tune "Sleep Walk" as a tribute to the lost musicians. The crash occurred on Feb 3, 1959 (and one would assume the radio news announcement was within 24 hours of the crash). The song "Sleep Walk" was not released until July 1959.
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Mistakes
When Ritchie is playing in the country bar, Bob's drumming is inconsistent with the drum sounds. See more...
La Bamba mistakes
Audio problem: When Ritchie is playing in the country bar, Bob's drumming is inconsistent with the drum sounds.
Continuity: When Ritchie's brother lies down next to him in his bed, the covers are down to Ritchie's stomach whenever they show him in a solo shot, but are pulled up almost to his neck when the shot shows both brothers together. In the next solo shot of Ritchie, the covers are back near his stomach again.