Function can't access Label

I have two function that use a UIDocument Label

public class UIController : MonoBehaviour
{
    private Label argentTexte;

    private int currentInt;
    private string currentString;

    void Start()
    {
        var root = GetComponent<UIDocument>().rootVisualElement;

        argentTexte = root.Q<Label>("currentMoney");
        Debug.Log(argentTexte.text); //<- show some string
    }

    public void IncreaseMoney(int moneyToAdd)
    {
        currentString = GetComponent<UIDocument>().rootVisualElement.Q<Label>("currentMoney").text; // Don't show anything, throw error
        Debug.Log(argentTexte.text); //throw an NullReferenceException: Object reference not set to an instance of an object
        int.TryParse(currentString, out currentInt);
        argentTexte.text = $"{currentInt + moneyToAdd}";
    }
    
public void DecreaseMoney(int moneyToDecrease)
    {
        currentString = GetComponent<UIDocument>().rootVisualElement.Q<Label>("currentMoney").text; // show some string
        int.TryParse(currentString, out currentInt);
        argentTexte.text = $"{currentInt - moneyToDecrease}";
    }
}

DecreaseMoney() is used on an object when i spawn it and it work, IncreaseMoney() is used on a child of an object when its destroyed and doesn't work.

Why DecreaseMoney() have access to argentTexte.text and not IncreaseMoney() ?