CS – No such Rambam exists.
In fact, the Rambam in Hilchois Shgagiyos clearly says that if someone’s Rebbe (or even the Sanhedrin) pasken something that you know is wrong, it is ASSUR for someone to follow that psak.
A dead Mashiach and a fake navi both clearly fit this bill.
What happened to the Daas in Chabad?!!