LookAt script locks Z axis when parent is rotated

I'm using a simple LookAt script but the Z rotation gets locked when it's Parent is rotated 90 degrees on the Z axis.

Here's my script

 using UnityEngine;
 // This complete script can be attached to a camera to make it
 // continuously point at another object.
 
 public class PointAt : MonoBehaviour
 {
     public Transform target;
 
     void Update()
     {
         // Rotate the camera every frame so it keeps looking at the target
         transform.LookAt(target);
 
         // Same as above, but setting the worldUp parameter to Vector3.left in this example turns the camera on its side
         transform.LookAt(target, Vector3.left);
     }
 }