Let’s see. The character moves up when the animation plays, but root motion seems to not be the effector. I assume you went to the correct animation referenced by the montage and changed it’s settings there, saved and compiled, then tested with no solution. It’s also possible that the way the animation was imported changed something about it.
There could still be something with the animation, for example, the hip bone moves up. Typically the hip bone has influence on the entire model. You can turn on bones in the animation view to see if the root or hip bone moves in such a way.
Otherwise it comes to something in code that is creating the problem, which I’m unaware of. At that point, its a number of guesses as to why, unless someone else has experienced something so similar. It could even be something unrelated, but it’s hard to say without seeing it all. Keep trying, otherwise try a different animation.