In the chord in the middle of the bar, Chopin overlooked the 
returning b in A. However, two notes later he added a cautionary natural before a (arranged a little bit too high).
Compare the passage in the sources »
category imprint: Interpretations within context; Differences between sources
issues: Omissions to cancel alteration, Errors of A, Authentic corrections of FE, Accidental below/above the note, Last key signature sign
notation: Pitch