[Bug] NullReferenceException Não conseguir identificar

Verifiquei tudo fiz e refiz e não entendi o porquê do erro. Não enviei tudo de cada script por que não coube.

NullReferenceException: Object reference not set to an instance of an object BossBehaviour.StartChasing () (at Assets/Scripts/Enemy/Boss/BossBehaviour.cs:118) GameManager.ActivateBossBehaviour () (at Assets/Scripts/GameManager.cs:80) BossFightTrigger.OnTriggerEnter2D (UnityEngine.Collider2D other) (at Assets/Scripts/Devices/BossFightTrigger.cs:13)

    public void StartChasing()
    {
        _Animator.SetBool("CanChase", true);
    }

    [Header("Dynamic game objects")]
    [SerializeField] private GameObject bossGate;
    [SerializeField] private PlayerBehavior _PlayerBehaviour;
    [SerializeField] private BossBehaviour _BossBehaviour;
    [SerializeField] private BossFightTrigger _BossFightTrigger;

    private void Awake()
    {
        if (Instance != null) Destroy(this.gameObject);
        Instance = this;

        _inputManager = new InputManager();

        TotalKeys = FindObjectsOfType<CollectableKey>().Length;
        _UIManager.UpdateKeysLeftText($"{KeysCollected}/{TotalKeys}");
        
        _BossFightTrigger.OnPlayerEnterBossFight += ActivateBossBehaviour;
    }

    private void ActivateBossBehaviour()
    {
        _BossBehaviour.StartChasing();
    }

using System;
using UnityEngine;

[RequireComponent(typeof(BoxCollider2D))]
public class BossFightTrigger : MonoBehaviour
{
    public event Action OnPlayerEnterBossFight;

    private void OnTriggerEnter2D(Collider2D other)
    {
        if(other.CompareTag("Player"))
        {
            OnPlayerEnterBossFight?.Invoke();
        }
    }
}