A band, a famous rock band (The Beatles), decides about pressing probably their last LP. During the recording they don?t get along, but at last they publish it and they break up. The LP is a smash.

1969, I do believe the horse had bolted by then. To stop them becoming legends it would have to be 1963.

To me this sentence doesn't make sense grammatically, either.
Back to the drawing board!

This does not work as a logline. It's too vague. I'd recommend reviewing the process of creating loglines. Who is the protagonist? What is their goal? What, or who, is the antagonist?