In A there are no accidentals to the first L.H. octave, while the 
lowering a to a
is only just before the 2nd crotchet. Chopin's mistake is evidenced by the 
before the bottom note of the last octave in this bar, which would be irrational if the 1st octave were supposed to be A-a (naturally, the mistake is also evidenced by the logic of the chromatic bass sequence). The mistake of A was carefully corrected by FE (→GE,EE) – flats were added to the 1st octave and the consequently superfluous accidental to a in the 2nd crotchet was removed.
Compare the passage in the sources »
category imprint: Interpretations within context; Differences between sources
issues: Omission of current key accidentals, Errors of A, Authentic corrections of FE, Last key signature sign
notation: Pitch