how to access a script, and affect only one of the gameobjects its attached to?

I have this huge problem. Even my teacher cant figure this one out. I basicly have my character spawning gadgets, which has a sperical collider that defines its range. The gadget puts nearby gameobjects with the tag "obstacle" in a 'stasis' mode. (stops the animation and sets the rigidbody to kinematic) Now, that works perfectly. The problem comes when I remove my gadget again. The gadget disapears and all is great but if it has stopped an "obstacle". The "obstacle doesnt restart the animation and the rigidbody stays kinematic. All I get in the Log is a NullRefferenceException.

The code consists of 3 scripts:

This first script is attached to all of my "obstacles":

     using UnityEngine;
 using System.Collections;
 public class Private_position_Update : MonoBehaviour {
     
     public Vector3 pos;
     public Quaternion rot;
     Quaternion rigRot;    
 
     void Start () 
     {
         pos = transform.position;
         rot = transform.rotation;
         rigRot = rigidbody.rotation;
     }
     void UseTime()
     {
         transform.position = pos;
         transform.rotation = rot;
         rigidbody.velocity = new Vector3(0,0,0);
         rigidbody.rotation = rigRot;
         rigidbody.angularVelocity = new Vector3(0,0,0);
         animation.Stop();
         animation.Play();
         rigidbody.isKinematic = false;    
     }
     public void RemoveOfGadget()
     {
         Debug.Log("Restart the animation and kinematicness");
         animation.Play();
         rigidbody.isKinematic = false;
     }
 }

This next script is attached to my gadget:

     using UnityEngine;
 using System.Collections;
 
 public class Pickupgadget_Reciver : MonoBehaviour {
 
     public GameObject ThisGameobject;
     public Private_position_Update PrivatePositionUpdate;
     
     void Awake(){
 
     }
     void PickMeUp()
     {
         Destroy(ThisGameobject);
         PrivatePositionUpdate.RemoveOfGadget();
     }
 }

And last one is also attached to my gadget and is the script that puts the "obstacles" in 'stasis'

     using UnityEngine;
 using System.Collections;
 
 public class StasisColliderStasis : MonoBehaviour {
     
     private Pickupgadget_Reciver PickupScript;
     public GameObject Target;
     public bool status;
     
     void Awake(){
         status = false;
     }
     
     void Start()
     {
         PickupScript = gameObject.GetComponent<Pickupgadget_Reciver>() as Pickupgadget_Reciver;
     }
     //The collider defines the range of the device.
     void OnTriggerStay (Collider other)
     {    
         //if the "intruder" has the tag "obstacle". It'll freeze position and rotation 
         if (other.transform.tag == "obstacle")
         {
             Debug.Log("I see you! >:D - " + other.transform.name);
                 if (other.rigidbody != null)
                 {
                     other.rigidbody.isKinematic = true;
                 }
                 if (other.animation    != null)
                 {
                 other.animation.Stop();    
                 }
         }
     }}
 

EDIT: I've changed the StasisColliderStasis script to OnTriggerEnter and OnTriggerExit

 using UnityEngine;
 using System.Collections;
 
 public class StasisColliderStasis : MonoBehaviour {
     
     private Pickupgadget_Reciver PickupScript;
     public GameObject Target;
     public bool status;
     
     void Awake(){
         status = false;
     }
     
     void Start()
     {
         PickupScript = gameObject.GetComponent<Pickupgadget_Reciver>() as Pickupgadget_Reciver;
     }
     //The collider defines the range of the device.
     void OnTriggerEnter (Collider other)
     {    
         //if the "intruder" has the tag "obstacle". It'll freeze position and rotation 
         if (other.transform.tag == "obstacle")
         {
             Debug.Log("I see you! >:D - " + other.transform.name);
                 if (other.rigidbody != null)
                 {
                     other.rigidbody.isKinematic = true;
                 }
                 if (other.animation    != null)
                 {
                 other.animation.Stop();    
                 }
         }
     }
     void OnTriggerExit (Collider other)
     {
         if (other.transform.tag == "obstacle")
         {
             if (other.rigidbody != null)
                 {
                     other.rigidbody.isKinematic = false;
                 }
                 if (other.animation    != null)
                 {
                 other.animation.Play();    
                 }
         }
     }
 }