WHY *PENDICARE - PENCHER, BUT MANDUCARE - MANGER? (Pourquoi *pendicare - pencher, mais manducare - manger?)

In French, there is a contradiction in the change that can be exemplified by two items: *pendicare -> pencher and manducare -> manger. Hans Rheinfelder, Gaston Zink and Michael Mazzola put forward various hypotheses to reconcile how the voiced palatal could be explained for manger, but the voiceless palatal for pencher both from an original intervocalic (k). According to the present writer, pencher is regular, whereas manger is to be accounted for by what he calls irregular sound change due to frequency.