How do I get a singleton to work after unity hot reloads?

I got a timer manager class that managers all of the timers in my game. It's a singleton and all of my other classes refer to it by it's Instance. But as soon as I do a hot reload, the other classes sees a reloaded instance but I think it's a new instance that the other classes are refering to. Does anyone know how to fix this?

My Code:

 //*****************************************************************************
 // Timer data class
 //*****************************************************************************
 [Serializable]
 public class Timer
 {
     public float defaultTime;
     public float curTime;
     public bool  paused;
     public bool  isDone;
 }
 
 //*****************************************************************************
 // Timer manager
 //*****************************************************************************
 public class TimerManager : MonoBehaviour
 {
     private static TimerManager _instance = null;
 
     [SerializeField]
     private List<Timer> timers = new List<Timer>();
     
     // Start is called before the first frame update
     void Awake()
     {
         if (!_instance)
             _instance = this;
         else
             DestroyImmediate(this);
 
         DontDestroyOnLoad(_instance.gameObject);
     }
 
     private void OnEnable()
     {
         if (!_instance)
             _instance = (TimerManager)FindObjectOfType<TimerManager>();
     }
 
     // Update is called once per frame
     void Update()
     {
         UpdateTimers();    
     }
     
     private void UpdateTimers()
     {
         foreach (var timer in timers)
         {
             // Check if timer can work
             if (timer.paused || timer.isDone)
                 continue;
             
             // Update all timers
             timer.curTime -= Time.deltaTime;
 
             if (timer.curTime <= 0f)
             {
                 timer.isDone = true;
                 timer.paused = true;
 
                 timer.curTime = 0f;
             }
         }   
     }
     
     // Public Methods
 //    public static TimerManager Instance => _instance;
 
     public static TimerManager Instance
     {
         get
         {
 //            if (_instance)
                 return _instance;
         }
     }
 
     public Timer GetNewTimer( float seconds = 0f )
     {
 //        TimerData newTimer = new TimerData( seconds );
         Timer newTimer = new Timer()
         {
             defaultTime = seconds,
             curTime = seconds,
             paused = true,
             isDone = false
         };
 
         timers.Add( newTimer );
 
         return newTimer;
     }
 
     public void Delete( Timer timer )
     {
         if (timers.Contains( timer ))
             timers.Remove( timer );
         
 //        timer.Dispose()
 //        timer = null;
     }
 
     public void Go( Timer timer )
     {
         timer.paused = false;
     }
 
     public void Pause( Timer timer )
     {
         timer.paused = true;
     }
 
     public void Set( ref Timer timer, float seconds )
     {
 //        if (!timers.Contains( timer ))
 //            return;
 //
 //        TimerData reftimer = timers.( timer );
 
 
         timer.curTime = timer.defaultTime = seconds;
         timer.paused = true;
         timer.isDone = false;
     }
     
     public void Reset( Timer timer )
     {
         timer.paused = true;
         timer.isDone = false;
         timer.curTime = timer.defaultTime;
     }
 }