Script acting weirdly after updating from 2018.2.2 to 2018.3.1

Everything was working fine util I updated to Unity 2018.3.1. Here you can see my player script. The problem is when a player die, he dies on the instance of the player who kills him, but is still alive in his instance. And when he respawns he sometimes respawn with over 100 hp or less.This scripts is attached to the player with a networkIdentity:

     using UnityEngine;
     using UnityEngine.Networking;
     using System.Collections;
     public class Player : NetworkBehaviour {
         public int MaxHealth = 100;
       [SyncVar]
         private bool _isDead = false;
         public bool isDead
         {
             get { return _isDead; }
             protected set { _isDead = value; }
         }
         [SerializeField]
         private Behaviour[] DisableOnDeath;
         [SerializeField]
         private GameObject[] DisableGameObjectsOnDeath;
         private bool[] wasenabled;
         public void PlayerSetup() {
     wasenabled = new bool[DisableOnDeath.Length];
             for (int i = 0; i < wasenabled.Length; i++)
             {
                 wasenabled[i] = DisableOnDeath[i].enabled;
     
             }
             SetDefaults();
         }
         public void SetDefaults()
         {
             isDead = false;
             CurrentHealth = MaxHealth;
             for (int i = 0; i < DisableOnDeath.Length; i++)
             {
                 DisableOnDeath[i].enabled = wasenabled[i];
             }
             //Enable GameObjects
             for (int i = 0; i < DisableGameObjectsOnDeath.Length; i++)
             {
                 DisableGameObjectsOnDeath[i].SetActive(true);
             }
             Collider col = GetComponent<Collider>();
             if (col != null)
             {
                 col.enabled = true;
             }
             Playerui.SetActive(true);
             //Make SpawnEffect  
                     GameObject gfxIns = Instantiate(SpawnEffect, transform.position, Quaternion.identity);
                    Destroy(gfxIns, 3f);
                 
         }
     [ClientRpc]
         public void RpcTakeDamage(int amount)
         {
             if (isDead)
                 return;
             CurrentHealth -= amount;
             Debug.Log(transform.name + " has now " + CurrentHealth + " health");
             if (CurrentHealth <= 0)
             {
                 Die();
             }
         }
         IEnumerator Respawn()
         {
             yield return new WaitForSeconds(GameManager.instance.matchSettings.RespawnDelay);
             Transform _startpoint = NetworkManager.singleton.GetStartPosition();
             transform.position = _startpoint.position;
             transform.rotation = _startpoint.rotation;
             yield return new WaitForSeconds(0.1f);
             SetDefaults();
             Debug.Log(transform.name + " Respawned");
         }
     public void Die()
         {
             isDead = true;
     
             //DisableComponenents
             for (int i = 0; i < DisableOnDeath.Length; i++)
             {
                 DisableOnDeath[i].enabled = false;
             }
             //DisableGameObjects
             for (int i = 0; i < DisableGameObjectsOnDeath.Length; i++)
             {
                 DisableGameObjectsOnDeath[i].SetActive(false);
             }
             //Disable the collider
             Collider col = GetComponent<Collider>();
             if (col != null)
             {
                 col.enabled = false;
             }
             Playerui.SetActive(false);
             Debug.Log(transform.name + " is dead");
              //SpawnDeathEffect
             GameObject gfxIns = Instantiate(deathEffect, transform.position, Quaternion.identity);
             Destroy(gfxIns, 3f);
             //Call respawn method;
             StartCoroutine(Respawn());
             }}