Asked the shaila myself.
There is a third group called “Elo-k-istim” who believe that not only the rebbe Moshiach, he is domeh to Hashem himself.
If the rabbi is a Meshichist most reliable Litvish poskim agree that though the Meshichist might be delusional or kookoo, there’s no problem.
Meshichist= No Problem Elo-K-ist=PROBLEM