AddListener in a loop only running once


I am quite a beginner at Unity and at C#, but that’s actually the first time I need to ask a question.
So I have this bit of code :

   public class InvWindow : MonoBehaviour
	GameObject itemButton;
	Inventory playerInventory;
    private void Start()
		itemButton = this.transform.Find("ItemButton").gameObject;
		playerInventory = this.transform.parent.parent.Find("MainBody").GetComponent<Inventory>();
		// Creation of the contents
		int margin = 0;
		foreach (string key in playerInventory.inventory.Keys) {
			GameObject instance = Instantiate(itemButton, this.transform); // create a entry
			Vector3 position = instance.transform.localPosition;
			// change game object name to make it unique _ DOES NOT FIX THE ISSUE = ("itemButton_" + margin);
			// These four lines move the button down each time one is created
			position.y =+ margin;
			instance.transform.localPosition = position;
			margin =+ 30;
			// Set appropriate name
			instance.transform.Find("Text").GetComponent<Text>().text = key;
			// Create button interaction
			instance.GetComponent<Button>().onClick.AddListener(() => ItemClicked(key));
	private void ItemClicked(string name)
		Debug.Log("Brrrt! Clicked on " + name);

It is supposed to read from a HashTable, and create a functional inventory window by instantiating the prefab button “itemButton” for each item.
Currently the table has two entries, and everything works fine, two buttons are created with the proper renaming.
However the AddListener bit only works for the first button (the argument is passed correctly), the second one is not clickable at all.

I’ve seen similar problems on Internet, but nothing I tried fixed this. What am I doing wrong?

I see.
This has been a great help.