player has two when speed increase in endless runner game

I am trying to make an endless runner game and I have set the player controller function as such

public class PlayerMotor : MonoBehaviour { private const float LANE_DISTANCE = 2.0f; //Movement private CharacterController controller; private float jumpForce = 4.0f; private float gravity = 12.0f; private float verticalVelocity; private float speed = 5.0f; //Which lane suppose to be private int desiredLane = 1; //0-Left, 1-Middle, 2-Right // private Vector3 moveVector; private float animationDuration = 3.0f; private bool isDead = false; private float startTime; // static public bool pauseCheck=true; void Start() { controller = GetComponent<CharacterController> (); startTime = Time.time; } //is called on every frame of the game void Update() { if (isDead) return; //calling to behave this way EVERYTIME scene is loaded or called // if (Time.timeSinceLevelLoad < animationDuration) if (Time.time - startTime < animationDuration) { //disable player controller on animation start up controller.Move (Vector3.forward * speed * Time.deltaTime); return; } // ----- // Gather inputs on which lane we should be if (Input.GetKeyDown(KeyCode.LeftArrow)) // Move Left MoveLane (false); if (Input.GetKeyDown(KeyCode.RightArrow)) //Move Right MoveLane (true); // Calculate where we should be in the future Vector3 targetPosition = transform.position.z * Vector3.forward; if (desiredLane == 0) targetPosition += Vector3.left * LANE_DISTANCE; else if (desiredLane == 2) targetPosition += Vector3.right * LANE_DISTANCE; // Let’s calculate our move delta Vector3 moveVector = Vector3.zero; moveVector.x = (targetPosition - transform.position).normalized.x * speed; // moveVector.y = -0.1f; moveVector.z = speed; // Moving character and optimizing on every device controller.Move (moveVector * speed * Time.deltaTime); // ------- controller.Move ((moveVector * speed) * Time.deltaTime); }

And the result that I got was that when the character is shifting to left or right it has a shadow like character beside it (basically another character beside but less vivid). Anyone know how to solve this issue that I am having?