The version of CLI without the Neapolitan chord was changed by Chopin in Ap, yet not in the base text for FE (differently as in analogous bar 17). Only in FEcor Chopin added the flats lowering b to b
and b1 to b1, yet both accidentals were put on the 2nd beat of the bar, as if b1 was still supposed to be in the 1st chord. It was probably a mistake, as in one of the subsequent proofreadings Chopin added a also at the beginning of the bar (the unnecessary on the 2nd beat of the bar was removed only in GE3 and subsequent GE,s).
Compare the passage in the sources»
category imprint: Differences between sources
issues: GE revisions, Accompaniment changes
notation: Pitch