update() keeps getting called with variable's old (initial) value, why wont the variable keep updated?

in my code I have a variable called ‘destination’, I initialize it in the ‘start()’ function and inside the function ‘ontriggerenter()’, and only inside that function do I update the value, regardless of that, my code seems to keep calling the update function with the original value of the variable (100s of times in a matter of seconds), and once a collision takes place it gets called with the value it should keep after ‘ontriggerenter’, but then keeps getting called with the original value, its like after the call to ‘ontriggerenter’ the variable gets changed back to its initial value, why would this happen?

plus I tried debugging the code but without having the stacktrace of the functions that call ‘update’, i have no way of finding the root of my problem, please help!

// here is my code! ===========================================

using System.Collections;
using System.Collections.Generic;
using System.Security.Cryptography;
using UnityEditor;
using UnityEngine;

public class ball_script : MonoBehaviour
    Rigidbody rb;
    [SerializeField] GameObject well_layer_prefab;
    [SerializeField] float speed = 0.005f;
    [SerializeField] Vector3 destenation;
    GameObject cam;
    [SerializeField] float speed_div = 2f;
    float lerpTime = 1f;
    float currentLerpTime;

    // Start is called before the first frame update
    void Start()
        rb = gameObject.GetComponent<Rigidbody>();
        cam = GameObject.Find("Main Camera");
        var currr = cam.transform.position;
        destenation = new Vector3(currr.x, currr.y, currr.z); // tried making a new vector just in case it doesnt get copied when assigned directly from currr

    // Update is called once per frame
    void Update()
        if (cam.transform.position.y < destenation.y)
            // problematic part !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
            // **problematic part** !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
            // problematic part !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

            print("tried to change to " + destenation.y+"pos is" + cam.transform.position);
        else if (cam.transform.position.y > destenation.y)
            // currentLerpTime += Time.deltaTime;
            // if (currentLerpTime > lerpTime)
            //    currentLerpTime = 0.125f;
            // }
            // float t = currentLerpTime;
            cam.transform.position = destenation;


    private void OnTriggerEnter(Collider other)
        float new_y_velocity = Mathf.Clamp(GetComponent<Rigidbody>().velocity.y / speed_div, -20f, -0.1f);
        GetComponent<Rigidbody>().velocity = new Vector3(0, new_y_velocity, 0);

        if (other.gameObject.tag == "goal")
            // get parent + play animation once + when done destroy
            if (other.gameObject.transform.parent)
                Animation anim = other.gameObject.transform.parent.GetComponent<Animation>();
                anim.wrapMode = WrapMode.Once;
                Destroy(other.gameObject.transform.parent.gameObject, .5f);

                //Vector3 cylinder_size = well_layer_prefab.transform.GetChild(0).gameObject.GetComponent<MeshRenderer>().bounds.size;

                // the only update part of destenation !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
                Vector3 shift_y = new Vector3(0, 0.6f, 0);
                destenation -= shift_y;


    void OnCollisionEnter(Collision collision)
        GetComponent<Rigidbody>().velocity = new Vector3(0,3,0);
        if (collision.gameObject.tag == "Finish")

        else { 
            // do nothing

In the end I want to add a link for my whole project if anyone needs
it, its very messy though, I apologize.
along with the project inside the zip file, there’s a video showing what I’m talking about
circle bouncer

If you want to be able to debug when it’s set, you could make a property like this

 Vector3 Destination
      get => destenation;
      set => destenation = value;

And then replace “destenation” with Destination everywhere in the document except when it is first declared. Then you could put a breakpoint on the line with set and attach the debugger so that it breaks when Destination is set.