Navmeshagens randomly just stop responging to commands.

I am creating a RTS game, were just randomly, after the units working perfectly fine, they just randomly clump togather and refuse to move were i click, even though just before they were fine. i have been trying to figure out why this is happening for weeks now with 0 luck. i have two diffrent scripts, one on the hostile units

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 using UnityEngine.AI;
 
 public class MoveToTarget : MonoBehaviour {
     
 
     public Transform goal;
 
     void Start()
     {
 
         
 
 
     }
 
     public void Update()
     {
         NavMeshAgent agent = GetComponent<NavMeshAgent>();
 
         Transform gameObject;
         gameObject = GameObject.FindGameObjectWithTag("PlayerUnit").transform;
 
 
         goal = gameObject;
 
         agent.destination = goal.position;
 
     }
 
    
 }

So this is fine, it finds the target and moves to it. but randomly, it just stops moveing while others are still moveing but one that just spawns does not move.

And this is in the units that the player can control

     public float RelaxDistance = 1;
 
     private NavMeshAgent agent;
     private Vector3 target = Vector3.zero;
     private bool selected = false;
     private bool isActive = false;
 
     public override void Deselect()
     {
         selected = false;
     }
 
     public override void Select()
     {
         selected = true;
     }
 
 
     public void SendToTarget(Vector3 pos)
     {
 
         target = pos;
         SendToTarget();
 
     }
 
     public void SendToTarget()
     {
         agent.SetDestination(target);
         agent.Resume();
         isActive = true;
     }
 
     // Use this for initialization
     void Start()
     {
         agent = GetComponent<NavMeshAgent>();
     }
 
     // Update is called once per frame
     void Update()
     {
         if (selected && Input.GetMouseButtonDown(1))
         {
             var tempTarget = RTSManager.Current.ScreenPointToMapPosition(Input.mousePosition);
             if (tempTarget.HasValue)
             {
                 target = tempTarget.Value;
                 SendToTarget();
             }
         }
 
         if (isActive && Vector3.Distance(target, transform.position) < RelaxDistance)
         {
             agent.Stop();
             isActive = false;
         }
     }

And this works, but same problem happens! THEY JUST STOP RESPONDING TO COMMANDS RANDOMLY!!!

i have were AI spawn to music, is that the cause? TO MENY NAVAGENS?!!?! this is driving me CRAZY!!!! <_>