Laws of Zaken Mamre and the Mesorah
One who disagrees with the Supreme Beis Din on a matter whose intentional commission is punishable by death (caret) and whose unintentional commission one must bring a sin offering, be it something they forbid and he permits or something they permit and he forbids, he is punishable by death, even if what he says is from tradition and he says 'I received this from my rabbis' and they say 'this seems reasonable to us.' Since he discusses the matter with them, if he acts or teaches to act [according to his opinion] he is liable."
It seems like Rambam is saying reason trumps mesorah!