More information is given by Wilhelm Fenner ,Chief at Division B of OKW/Chi (Cryptanalysis) in DF187B – ‘’The Cryptanalytic successes of OKW/Chi after 1938’’ , p7 :
Even before the military action with France began , the military systems of French higher staffs were solved.This was a 4 or 5-figure code that was systematically transposed (tableau carve) .In the cryptograms a few parallel passages (repetitions) were discovered .The interval between these passages was constant and must therefore correspond to the width of the transposition box as cryptanalytic studies have shown.If I am not mistaken the keys (Loesungen ? ? ? ) ? ? the box itself were taken from the same code book. Despite all the cunning of this cryptographic system, the occurrence of short parallel passages proved fatal. By the aid of these deciphered messages tabs could be kept on the French Army far back into the homeland.