源代码：

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class DestroyOutOfBound : MonoBehaviour
{
    // Start is called before the first frame update
    private float topBound = 40;
    private float lowerBound = -40;
    void Start()
    {
        
    }

    // Update is called once per frame
    void Update()
    {
        if (transform.position .z > topBound )
        {
            Destroy(gameObject);
        }
        else if(transform.position.z < lowerBound )
        {
            Destroy(gameObject);
        }
    }
}

解决方法：

一定要注意不要忘记应用到所有预制件上：override-> apply all