In Unity, my joystick button only works a few times, why?

Question

My part of the input code looks like this:

void Update()
{
    y_input = Input.GetButtonUp(StaticStrings.Y);

    delta = Time.fixedDeltaTime;
    states.Tick(delta);
    ResetInputNStates();
}

void GetInput()
{
    vertical = Input.GetAxis(StaticStrings.Vertical);
    horizontal = Input.GetAxis(StaticStrings.Horizontal);
    b_input = Input.GetButton(StaticStrings.B);
    a_input = Input.GetButton(StaticStrings.A);
    y_input = Input.GetButtonUp(StaticStrings.Y);
    x_input = Input.GetButton(StaticStrings.X);
    rt_input = Input.GetButton(StaticStrings.RT);
    rt_axis = Input.GetAxis(StaticStrings.RT);

    if (rt_axis != 0)
        rt_input = true;

    lt_input = Input.GetButton(StaticStrings.LT);
    lt_axis = Input.GetAxis(StaticStrings.LT);

    if (lt_axis != 0)
        lt_input = true;

    rb_input = Input.GetButton(StaticStrings.RB);
    lb_input = Input.GetButton(StaticStrings.LB);

    rightAxis_down = Input.GetButtonUp(StaticStrings.L) || Input.GetKeyUp(KeyCode.T);

    if (b_input)
        b_timer += delta;

    d_x = Input.GetAxis(StaticStrings.Pad_X);
    d_y = Input.GetAxis(StaticStrings.Pad_Y);

    d_up = Input.GetKeyUp(KeyCode.Alpha1) || d_y > 0;
    d_down = Input.GetKeyUp(KeyCode.Alpha2) || d_y < 0;
    d_left = Input.GetKeyUp(KeyCode.Alpha3) || d_x < 0;
    d_right = Input.GetKeyUp(KeyCode.Alpha4) || d_x > 0;
}

The problem is that my Y button is connected with the function of changing from one hand weapon to two hand weapon, but the Y button only works a few times in game!

e.g., I have to press about 3 times then it works.

How do I solve this?