It is apparent that the slur in GC is imprecise - it ends on the end of b. 398 (b.56), which was rightly corrected in GE by extending it over to the first crotchet. This diminshes GC (→GE) credibility and raises doubts as for the slur's beginning as well. Therefore, in the main text we adopt the consistent version of EE and FE.
Compare the passage in the sources »
category imprint: Differences between sources; Source & stylistic information
issues: GE revisions, Inaccuracies in GC
notation: Slurs