I'm have trouble with the ai script in standard asset

AI script taken from standard assets can only work in a short distance. I don't why this is happening, I am not an expert in 3d AI scripting. I just need someone to look it over and tell me what to remove or add in the script.

 [RequireComponent(typeof (UnityEngine.AI.NavMeshAgent))]
 [RequireComponent(typeof (ThirdPersonCharacter))]
 public class AICharacterControl : MonoBehaviour
 {
     public UnityEngine.AI.NavMeshAgent agent { get; private set; }             // the navmesh agent required for the path finding
     public ThirdPersonCharacter character { get; private set; } // the character we are controlling
     public Transform target;                                    // target to aim for


     private void Start()
     {
         
         // get the components on the object we need ( should not be null due to require component so no need to check )
         agent = GetComponentInChildren<UnityEngine.AI.NavMeshAgent>();
         character = GetComponent<ThirdPersonCharacter>();
         agent.updateRotation = false;
         agent.updatePosition = true;
         target = GameObject.FindGameObjectWithTag("Player 1").transform;

     }


     private void Update()
     {
         if (target != null)
             agent.SetDestination(target.position);

         if (agent.remainingDistance > agent.stoppingDistance)
             character.Move(agent.desiredVelocity, false, false);
         else
             character.Move(Vector3.zero, false, false);


     }


     public void SetTarget(Transform target)
     {
         this.target = target;
     }
 }