Hi,
Unfortunately there isn't a lot can be done in this case. The issue is due to the fact the unload process is blocking thus prevent the UI from refreshing. The blocking can occur in multiple places:
1. Inside the web page. For example, if the page has JavaScript code that responds to unload/resize event, then those code will be called and the UI will not repaint until those code finishes running;
2. If you have some event driving code that is called while the tab is switched, it will have the same effect;
The goal would be try to minimize such code so that the freeze period is short enough thus not visible. If any case, if you can isolate the problem into a repro project we will be happy to analyze it here too. See here for more information on sending test project to us:
https://www.essentialobjects.com/forum/test_project.aspxThanks!