Rigidbody bumping when going down slopes

My rigidbody controller goes fine up a slope, but when I go down it, it bumps around. My collider is smooth around the edges. I use Rigidbody.MovePosition to move the player.

What is happening?

No, isKinimatic is set to false. Also, how do I move on the local axis, not the global axis?

In the docs for MovePosition it states that in order for a smooth transition it needs to be kinematic but that would be used for something like for example a 3rd person platformer enemy. A rigidbody ideally needs AddRelativeForce.

Instead of using RigidBody.MovePosition alone. You can use a lerp function to make it smoother.

Rigidbody.MovePosition (Vector3.Lerp (rb.position, finishedMovement, 1f));

Alternatively you can move the object along the slope rather than the forward position.

HitInfo GetFloor() {
	// Do raycast to get floor
	Ray ray = new Ray (transform.position, vector3.down);
	HitInfo hit;
	Physics.Raycast (ray, out hit);
	return hit;

Vector3 GetMoveDirection () {
	var forward = transform.forward;
	var floor = GetFloor();
	if (floor.transform == null)
		return forward;
	var normal = floor.Normal;
	var moveDir = new Vector3 (forward.x, -normal.y, for .z);
	return moveDir.Normalize();

Vector3 movement = GetMoveDirection () * MovementInputValue * -moveSpeed * Time.deltaTime;
Vector3 finishedMovement = rb.position + movement;
if (whichMovement == movementType.rbMovePosition)
	rb.MovePosition(new Vector3(finishedMovement.x, transform.position.y, finishedMovement.z));
else if (whichMovement == movementType.rbAddRelativeForce)
	rb.MovePosition(new Vector3(finishedMovement.x, transform.position.y, finishedMovement.z));