I had the same kind of corrupted file error recently for the very first time after years of Max use. Triangles were simply disappearing at each edit I was trying to do... Same thing, rotating viewport crashed the app when I tried to reopen the file. The Max8 demo has been able to load the file almost fine, and I exported…
The triangle going through the middle of the face interferes with the cut tool. The more convex or concave it is, the more problems you will have. Planar faces work perfect every time. Resetting xforms will help, as will rotating the object to try a different angle. I found a plugin that made it work perfectly, but it was…