Redirect URL error

Hi,

I am using the following code to get request token post login:
Dim redirectURL As String = String.Format("http://{0}:{1}/", IPAddress.Loopback, GetRandomUnusedPort())
Dim loginURL As String = String.Format("{0}&redirect_url={1}", "https://kite.trade/connect/login?api_key=" & ApiKey & "&v=3", redirectURL)

Dim http = New HttpListener()
http.Prefixes.Add(redirectURL)
http.Start()
'Console.WriteLine("Waiting for login to finish")
Process.Start(New ProcessStartInfo(loginURL) With {
.UseShellExecute = True
})
Dim context = Await http.GetContextAsync()
.....

I pass a Random Port to the "kite.trade/connect" URL, like "http://127.0.0.1:51218/"

This was working fine until a few days back.
But now suddenly sometimes it works fine and sometimes it goes to "http://127.0.0.1/?action=login&type=login&status=success&request_token=433O8uWTcujM7Y7Vi7QrEJ2ADx2rkzRt" which is not accessible.

Some days it works fine, some days, it doesn't!!!!!

Can you help plug this one please?

Regards

Manoj