I'm experiencing a strange movement jitter with a CharacterController in Unity 6.

My player movement is handled entirely inside `FixedUpdate()`. The controller velocity is accumulated there and I call:

    controller.Move(velocity * Time.fixedDeltaTime);

The camera(CineMachine) is not the issue. I verified this by:

* not moving the mouse at all,
* slowing the game down with `Time.timeScale = 0.2`,
* watching the player move with damping.

When slowed down, I can clearly see that the player advances in tiny discrete jumps instead of moving smoothly.

The movement is implemented using a custom Quake/Source-style acceleration system with CharacterController. Code:

    private void FixedUpdate()
    {
        Move();
        ApplyCounterMovement();
        ApplyFriction();
        ApplyGravity();
    
        motor.Move(Time.fixedDeltaTime);
    }
    
    private void Move()
    {
        Vector2 moveInput = input.MoveInput;
        Vector3 wishDirection = GetWishDirection(moveInput);
    
        if (wishDirection.sqrMagnitude < 0.0001f)
            return;
    
        wishDirection.Normalize();
    
        float wishSpeed = isGrounded ? walkWishSpeed : airWishSpeed;
        float accel = isGrounded ? walkAcceleration : airAcceleration;
    
        Accelerate(wishDirection, wishSpeed, accel);
    }
    
    private void Accelerate(Vector3 wishDirection, float wishSpeed, float accel)
    {
        Vector3 horizontalVelocity = GetHorizontalVelocity();
        float currentSpeed = Vector3.Dot(horizontalVelocity, wishDirection);
    
        float addSpeed = wishSpeed - currentSpeed;
        if (addSpeed <= 0f)
            return;
    
        float accelSpeed = accel * Time.fixedDeltaTime * wishSpeed;
        accelSpeed = Mathf.Min(accelSpeed, addSpeed);
    
        motor.AddVelocity(wishDirection * accelSpeed);
    }
    
    private void ApplyCounterMovement()
    {
        if (!isGrounded)
            return;
    
        if (input.MoveInput.sqrMagnitude < 0.01f)
            return;
    
        Vector3 wishDirection = GetWishDirection(input.MoveInput).normalized;
        Vector3 horizontalVelocity = GetHorizontalVelocity();
    
        Vector3 unwantedVelocity =
            horizontalVelocity -
            Vector3.Project(horizontalVelocity, wishDirection);
    
        motor.AddVelocity(
            -unwantedVelocity *
            counterMovement *
            Time.fixedDeltaTime);
    }
    
    private void ApplyFriction()
    {
        if (!isGrounded)
            return;
    
        if (input.MoveInput.sqrMagnitude > 0.01f)
            return;
    
        Vector3 horizontalVelocity = GetHorizontalVelocity();
        float speed = horizontalVelocity.magnitude;
    
        float drop = groundFriction * Time.fixedDeltaTime;
        speed = Mathf.Max(speed - drop, 0f);
    
        horizontalVelocity = horizontalVelocity.normalized * speed;
    
        motor.SetVelocity(new Vector3(
            horizontalVelocity.x,
            motor.Velocity.y,
            horizontalVelocity.z));
    }
    
    private void ApplyGravity()
    {
        Vector3 velocity = motor.Velocity;
    
        if (isGrounded && velocity.y < 0f)
        {
            motor.SetVelocity(new Vector3(
                velocity.x,
                -groundStickVelocity,
                velocity.z));
            return;
        }
    
        motor.AddVelocity(Vector3.down * gravity * Time.fixedDeltaTime);
    }

PlayerMotor.Move() simply calls:

    public CollisionFlags Move(float deltaTime)
    {
        Vector3 moveVelocity = Velocity;
    
        if (IsGrounded && moveVelocity.y < 0f)
            moveVelocity.y = -2f;
    
        return controller.Move(moveVelocity * deltaTime);
    }

Help i have a movement jitter using CharacterController in Unity 6