FE has b1-f
2 as the 3rd quaver in the 5th group of the line, with the lower note having a natural, which is incomprehensible after b1 in the previous quaver. The notation also influences the pitch of the 1st quaver in the next group, in which c2 is the lower note, which, in turn, makes the before the next c2 superfluous. The anomalies in the notation, together with irregular progression of diminished four-note chords, enable to identify a mistake in this situation. That assumption is proven by the undoubtedly correct version of GE with c2-f2. In EE1 the version of FE was revised, eliminating the superfluous 
before the second b1, while the correct text was reintroduced only in EE2.
Compare the passage in the sources»
category imprint: Differences between sources
issues: EE revisions, Errors in FE
notation: Pitch