The version of the 2nd half of the bar in A, pianistically and harmonically questionable, is probably an example of a "correction" (the change of 
to 
, probably performed in a hurry), which resulted in a greater mistake than the one that was supposed to be corrected – the absence of the restoring b
on the 5th quaver. The initial notation reveals that Chopin approached this place in the same way as he did with the similar situations in bar 254 (as well as 250 and 253), where the flats, although undoubtedly necessary, are only of a cautionary nature.
In GE (→FE,EE,IE) the initial text was restored, supplemented by the necessary .
category imprint: Interpretations within context; Differences between sources
issues: Corrections in A, Errors resulting from corrections, GE revisions, Foreign hand additions in manuscripts, Deletions in A
notation: Pitch