In the 2nd half of the bar there are no accidentals before the 2nd and 4th bottom voice quavers in A (→FC,FE→EE1). It must be an oversight of Chopin, who, in his mind, changed the key to D
major as the notation of g
turned to a. The necessary accidentals were added in GE and EE2; in turn, the incomplete notation was not problematic for the pupils, since none of the teaching copies contains annotations here.
The 
visible in FC before the last quaver was added later.
Compare the passage in the sources»
category imprint: Interpretations within context; Differences between sources
issues: EE revisions, GE revisions, Omission of current key accidentals, Errors of A, Errors repeated in FE
notation: Pitch