Character controller move not working

Hi, I am having a problem with the Character controllers move function. Using this code(straight from the example):

    public float speed = 6.0F;
     public float jumpSpeed = 8.0F;
     public float gravity = 20.0F;
     private Vector3 moveDirection = Vector3.zero;
     void Update() {
         CharacterController controller = GetComponent<CharacterController>();
         if (controller.isGrounded) {
             moveDirection = new Vector3(Input.GetAxis("Horizontal"), 0, Input.GetAxis("Vertical"));
             moveDirection = transform.TransformDirection(moveDirection);
             moveDirection *= speed;
             if (Input.GetButton("Jump"))
                 moveDirection.y = jumpSpeed;
             
         }
         moveDirection.y -= gravity * Time.deltaTime;
         controller.Move(moveDirection * Time.deltaTime);
     }

When i press both down arrow key and either left or right arrow key( or s and a or d) the character moves diagonally however when the up arrow key and either left or right arrow key the character does not move diagonally but just sideways.

Is there a known bug with the character controllers move or am I doing something wrong?

EDIT: I solved the issue. My character had a cube representing the front of it(its just a capsule) and I forgot to remove the collider off this cube so when moving forward there were weird collision issues.