I think the issue is due to the cache.
The dialoge displays the previous cached page again.
You can try by clearing the history/cache of the browser.
To implement in the page, you must clear the cache in the page load event of the dialoge box.
Try using this code (ASP .net C#)
HttpContext.Current.Response.Cache.SetCacheability(HttpCacheability.NoCache);
HttpContext.Current.Response.Cache.SetExpires(DateTime.Now - new TimeSpan(1, 0, 0));
HttpContext.Current.Response.Cache.SetLastModified(DateTime.Now);
HttpContext.Current.Response.Cache.SetAllowResponseInBrowserHistory(false);