I just want to get one thing clear since both you and others have written thing which seem to be cotradictory and I must be misunderstanding some nuance of it. Do you agree or deny that there are some extreme fringes of Lubavitch who have gone to extremes which seem to be apikursus or very close to it?
I was in a Litvish mosad for 9 years and heard all about how Chabad isn't Judaism.
I then spent 8 years in Chabad mosdos, some anti-meshichist, some meshichist, and I've never encountered anyone or anything that could remotely be construed as apikorsos.
I've always heard rumors of a few wacko "elokistim" that live in Tzfas. But if such people do exist, they are the .0001% loons that exist in every walk of life.
Most people take issue with the belief that the Rebbe could be moshiach, not of 3 loons in Tzfas. And people who think that there is any connection to apikorsus c"v or Shabsai Tzvi (who blatantly violated halacha) are simply ignorant of actual halacha.