Player with Rigidbody gravity and root motion bobs up and down into the terrain

I have a player that uses a mecamin humanoid rig with root motion applied and has a rigidbody with UseGravity checked. Also, the Root Transform Position (Y) is set to Bake into pose based on feet for the idle, walk, and run animation clips. And all of this works with no problems on a flat surface. It even works most of the time on hills. However, there are times on hills with slightly sharp changes in slope that the player will dip down into the terrain and then bob up and continue in this fashion indefinitely until I start walking again, then the player seems to settle back to the right elevation - on top of the terrain. Is there anyway to fix this without resorting to using a CharacterController instead of a rigidbody? I also really need the root motion as this model is set up to walk realistically with root motion. I'm using Unity 5.2.0f3 Personal.