Fps OpenGL issues

Hi,

i noticed a strange Fps problem.

I cant see the unlimited FPS in my “Monogame Windows OpenGL Project”. It stuck by 60 FPS
In the DirectX version it works fine.

public class Game1 : Game
    {
        GraphicsDeviceManager graphics;
        SpriteBatch spriteBatch;
        SpriteFont font;
        public Game1()
            : base()
        {
            graphics = new GraphicsDeviceManager(this);
            Content.RootDirectory = "Content";
            graphics.SynchronizeWithVerticalRetrace = false;
            IsFixedTimeStep = false;
        }

        /// <summary>
        /// Allows the game to perform any initialization it needs to before starting to run.
        /// This is where it can query for any required services and load any non-graphic
        /// related content.  Calling base.Initialize will enumerate through any components
        /// and initialize them as well.
        /// </summary>
        protected override void Initialize()
        {
            // TODO: Add your initialization logic here
            
           
            base.Initialize();
        }

        /// <summary>
        /// LoadContent will be called once per game and is the place to load
        /// all of your content.
        /// </summary>
        protected override void LoadContent()
        {
            // Create a new SpriteBatch, which can be used to draw textures.
            spriteBatch = new SpriteBatch(GraphicsDevice);
            font = Content.Load<SpriteFont>("Arial");
            // TODO: use this.Content to load your game content here
        }

        /// <summary>
        /// UnloadContent will be called once per game and is the place to unload
        /// all content.
        /// </summary>
        protected override void UnloadContent()
        {
            // TODO: Unload any non ContentManager content here
        }

        /// <summary>
        /// Allows the game to run logic such as updating the world,
        /// checking for collisions, gathering input, and playing audio.
        /// </summary>
        /// <param name="gameTime">Provides a snapshot of timing values.</param>
        int _total_frames = 0;
        float _elapsed_time = 0.0f;
        int _fps = 0;
        protected override void Update(GameTime gameTime)
        {


            _elapsed_time += (float)gameTime.ElapsedGameTime.TotalMilliseconds;

            // 1 Second has passed
            if (_elapsed_time >= 1000.0f)
            {
                _fps = _total_frames;
                _total_frames = 0;
                _elapsed_time = 0;
            }
            if (GamePad.GetState(PlayerIndex.One).Buttons.Back == ButtonState.Pressed || Keyboard.GetState().IsKeyDown(Keys.Escape))
                Exit();

            // TODO: Add your update logic here

            base.Update(gameTime);
        }

        /// <summary>
        /// This is called when the game should draw itself.
        /// </summary>
        /// <param name="gameTime">Provides a snapshot of timing values.</param>
        protected override void Draw(GameTime gameTime)
        {
            GraphicsDevice.Clear(Color.CornflowerBlue);
            _total_frames++;
            // TODO: Add your drawing code here
            spriteBatch.Begin(SpriteSortMode.Immediate, null, null, null, null, null);
            spriteBatch.DrawString(font, _fps.ToString(), Vector2.Zero, Color.Yellow);
            spriteBatch.End();
            base.Draw(gameTime);
        }
    }

Used the same code…
Just started with Monogame one week ago, it should be the lastest build.