Exception error using windows forms in a thread

I have a candle countdown Bot that uses windows forms.  I has twice given me an error.

I pretty much got the code from a thread on this forum.  Is there any reason you can think of that this would occur?  See code below.

using cAlgo.API;
using System.Threading;
using System.Windows.Forms;
using System;

namespace cAlgo.Robots
{
    [Robot(TimeZone = TimeZones.UTC, AccessRights = AccessRights.FullAccess)]
    
    public class myCandleCountDown : Robot
    {
        [Parameter("Alert On", DefaultValue = true)]
        public bool paramAlertOn { get; set; }
        [Parameter("Always On Top", DefaultValue = true)]
        public bool paramOnTop { get; set; }

        private Thread _thread;
        private frmCandleCountdown _counter;
        readonly string alertFile = Environment.GetFolderPath(Environment.SpecialFolder.Personal) + @"\cAlgo\Sources\Robots\CountdownTimer.wav";
        
        protected override void OnStart()
        {
            Timer.Start(1);
            _counter = new frmCandleCountdown(this, paramOnTop);
            _thread = new Thread(() =>{ _counter.ShowDialog(); });
            _thread = new Thread(() => { Application.Run(_counter); });
            _thread.SetApartmentState(ApartmentState.STA);
            _thread.Start();    
        }

        protected override void OnTimer()
        {
            int cdMinutes = 14 - Time.Minute % 15;
            int cdSeconds = 59 - Time.Second;
            _thread = new Thread(() =>{ _counter.UpdateCounter(cdMinutes.ToString("00")+":"+cdSeconds.ToString("00"));});
            _thread.SetApartmentState(ApartmentState.STA);
            _thread.Start();
            if (cdMinutes==1 && cdSeconds==0 && paramAlertOn)
            {
                System.Media.SoundPlayer player = new System.Media.SoundPlayer(alertFile);
                player.Play();
            }
        }
         
        protected override void OnStop()
        {
            _thread = new Thread(() => {_counter.Close();});
            _thread.SetApartmentState(ApartmentState.STA);
            _thread.Start();
        }
    } 
}