Before the 7th semiquaver in A there was initially a 
(cautionary due to B
(1) in the L.H.), which Chopin turned to a 
. Fontana and the engraver of FE1 misinterpreted that correction by considering it a deletion of the accidental, hence FC (→GE) and FE1 does not contain any accidental before that note, which gives b
1. When the figure is repeated an octave higher (at the beginning of b. 23) in FC (→GE), there is also no , which can be explained by an oversight (it would be a puzzling coincidence!) or by a revision, introduced in the belief that it is also here that the alleged crossing-out from b. 22 should be taken into account.
In both places, the naturals visible over the notes were added in FC by H. Scholtz probably in the 1870s.
Compare the passage in the sources»
category imprint: Differences between sources; Corrections & alterations; Source & stylistic information
issues: Corrections in A, Errors resulting from corrections, FE revisions, Errors of FC
notation: Pitch