Character movement problem, floats away

Hi guys,

I'm creating a top down game and I have a weird control problem.

Every time I press a movement key (W,A,S,D) or release a movement key, the player character moves slightly upwards away from the ground (+ve Y direction). He just floats away bit by bit.

I've added a Player object with a ChracterController and no rigid body.

I've added the following movement script:

     public class PlayerMovement : MonoBehaviour
     {
     public float Speed = 6.0f;
         
     private Vector3 _moveDirection = Vector3.zero;
 
     // Use this for initialization
     void Start () {
     
     }    
     // Update is called once per frame
     void Update () {
 
         CharacterController controller = GetComponent<CharacterController>();
 
         _moveDirection = new Vector3(-1 * Input.GetAxis("Vertical"), 0, Input.GetAxis("Horizontal"));
         _moveDirection *= Speed;
         
         controller.Move(_moveDirection * Time.deltaTime);                
     }
 }

I'm doing camera relative movement, not character relative.

This script works fine except the unexpected Y movement on each key down and release. I'm sure I'm making a dumb noob mistake! :)

If I use transform.Translate() this problem does not occur, but then collisions don't work properly.

125][1]125