Odd Rotation Behavior

1. I have a player character that rotates towards a gameObject tied to mouse position, but only on the y axis. This behavior works great.

2. Childed to the player character are two lights that should only rotates towards the mouse position on the x axis. This behavior works great --half the time.

Gif of issue

3.It seems that whenever the world rotation of the lights goes below -90 and above 90, it flips. I've tried to add a case for this, but it didn't seem to work.

1. Here's my code. I'm not a smart man, so if you see an obvious math issue or a better way of doing this, please let me know.

Code (CSharp): void Update() {

     parentRotation = transform.rotation.y;
     Vector3 dir = target.position - transform.position;
 
     dir.Normalize();
 
     switch (constraint)
     {
 
         case Constraint.None:
             gameObjectLocation = new Vector3(transform.position.x, transform.position.y, transform.position.z);
             targetLocation = new Vector3(target.position.x, target.position.y, target.position.z);
 
             Vector3 direction = targetLocation - gameObjectLocation;
             Quaternion rotation = Quaternion.LookRotation(direction);
             transform.rotation = Quaternion.Lerp(rotation, rotation, speed * Time.deltaTime);
 
             break;
 
         case Constraint.X:
                 rotationX = (Mathf.Atan2(-dir.y, dir.z) * Mathf.Rad2Deg);
                 rotationX = Mathf.Clamp(rotationX, -maxXRotation, maxXRotation);
                 transform.localRotation = (Quaternion.RotateTowards(transform.localRotation, Quaternion.Euler(rotationX, 0f, 0f), Time.deltaTime * speed));
      
             break;
 
         case Constraint.Y:
             rotationY = (Mathf.Atan2(dir.x, dir.z) * Mathf.Rad2Deg);
             rotationY = Mathf.Clamp(rotationY, -maxYRotation, maxYRotation);
             transform.localRotation = (Quaternion.RotateTowards(transform.localRotation, Quaternion.Euler(0f, rotationY, 0f), Time.deltaTime * speed));
             break;
 
         case Constraint.Z:
             rotationZ = (Mathf.Atan2(dir.y, -dir.x) * Mathf.Rad2Deg);
             rotationZ = Mathf.Clamp(rotationZ, -maxZRotation, maxZRotation);
             transform.localRotation = (Quaternion.RotateTowards(transform.localRotation, Quaternion.Euler(0f, 0f, rotationZ), Time.deltaTime * speed));
             break;
 
 
     }
 }