navigationBar strange resize

Hi.

In a form (maximized) I have a NavigationBar Left/Top/Bottom anchored and Left Docked.

With this event:

 private async void navigationBar1_ItemClick(object sender, Wisej.Web.Ext.NavigationBar.NavigationBarItemClickEventArgs e)
        {
            string k = e.Item.Tag.ToString();
            ShowLoader = true;
            await this.CheckLogin(true);
            ShowLoader = false;
            switch (k)
            {
                case "CHECKLIST":
                    FrmCL CL=null;    
                    if (CL == null) { CL = new FrmCL(); CL.Show(); }
                    break;
            }
            Wisej.Web.Application.Update(this); // update the client

        }

From the second click, the NavigationBar  seems to revert to the original height (desgin time height).

Only if I change the browser window size the NavigationBar  height returns to normal, but after 2 more Item clicks the height still returns incorrect