Some scripts not working after closing unity

I am using an older version of Unity for school, and when I close out of Unity, when I load back into it, one of my scripts doesn't work. Every time I have to remove and reapply the script for my game to work. My unity version is Unity 4. something, not sure with these school computers. If anyone has had a similar problem and found a fix, I would greatly appreciate the answer.

This script is attached to my main camera on the FPS controller. #pragma strict

var rayLength = 10;

private var treeScript : TreeController;

private var playerAnim : PlayerControl;

function Update() { var hit : RaycastHit; var fwd = transform.TransformDirection(Vector3.forward);

 if(Physics.Raycast(transform.position, fwd, hit, rayLength))
 {
     if(hit.collider.gameObject.tag == "Tree")
     {
         treeScript = GameObject.Find(hit.collider.gameObject.name).GetComponent(TreeController);
         playerAnim = GameObject.Find("FPSArms_Axe@Idle").GetComponent(PlayerControl);
         
         if(Input.GetButtonDown("Fire1") && playerAnim.canSwing == true)
         {
             treeScript.treeHealth -= 1;
         }
     }
 }

}