moving in y axis with nav mesh

hello, I have simple movement script that works very well in x and z, but when my object reaches target (which is in the air) it stops below it. how can I fix it? Thanks!

 using UnityEngine;
 using System.Collections;
 
 public class new_R : MonoBehaviour
 {
 
     public Transform t;
 
     public float timer;
     public int newtarget;
     public float speed;
     public NavMeshAgent nav;
     public Vector3 target;
 
 
     void Start()
     {
 
         nav = gameObject.GetComponent<NavMeshAgent>();
     }
 
     // Update is called once per frame
     void Update()
     {
         timer += Time.deltaTime;
         if (timer >= newtarget)
         {
             newtarget1();
         }
         timer = 0;
 
     }
     void newtarget1()
     {
         float myx = gameObject.transform.position.x;
         float myz = gameObject.transform.position.z;
 
 
    
         float xpos = t.position.x;
         float ypos = t.position.z;
         float zpos = t.position.z;
         target = new Vector3(xpos, ypos, zpos);
        
        
        nav.SetDestination(target);
     }
 }