In FE the 
before the 2nd quaver is misplaced: it should be before the bottom note (g
), not the top one (e1). The mistake possibly stemmed from the graphical similarity between b. 5 and 6. The correct accidental was added in FES, while FC (→GE) and EE not only added the right flat, but also removed the wrong one.
Compare the passage in the sources »
category imprint: Differences between sources
issues: EE revisions, Errors in FE, Fontana's revisions
notation: Pitch