In the sources, the cautionary 
at the beginning of the bar is before B
in the bass, yet it is absent before b2 in the R.H., where it is more justified. It seems that Chopin did not combine these two elements:
-
the sign in the R.H. did not seem to be necessary, same as the
returning g2 on the 3rd beat of this bar was overlooked – Chopin heard and wrote both voices independently. -
the sign in the L.H. was copied while correcting this note from the original d, which makes it a momentum error – the correction is proved by a visible deletion of this note (see also corrections in analogous bars 461-462).
In the main text we remove the in the L.H. and add it in the R.H.
Compare the passage in the sources »
category imprint: Editorial revisions; Corrections & alterations
issues: Corrections in A, Cautionary accidentals, Last key signature sign
notation: Pitch