I dont know why an animated character suddenly ends with legs under the ground and i can see just the upper part of the body. I saw the forums searching for a solution but none have worked, i set the animation to Root Transform position Y to bake into pose and feet, also tried to change the scale but with no luck. The rig is set to humanoid and the character makes all animations right but after some time goes suddently through the floor up to the waist and stays there
Take a look at the Collider of the character, it should touch the ground.
I had the same problem but my object was stuck in the floor all the time. I don’t know what 3d modelling app you’re using but I use Blender and it was because of the Blender FBX export settings. When exporting as a FBX in the animation settings I had all settings checked. After unchecking all settings except ‘Baked Animation’ and ‘All actions’ it works fine.
Some animations were wrong, i just used others, also in one case i had a transition with the wrong parameter and gave also the same failure making fall the character up to waist
Remember to set all of them to humanoid in the Rig → Animation Type. Because Humanoid and non-Humanoid Animations does not work.
Open your 3D Model in blender and export to fbx, now the animation should work.