You cant try using Dispatcher :
RadPane pane = e.Panes.ToList();
RadPaneGroup group = pane.PaneGroup;
e.Handled = true;
It seems like this fixes the issue in my test project. It would be great if you can see if this works for you.
Nevertheless the "Object reference not set to an instance of an object." exception should be fixed in the next LIB.
Hope this will help.
All the best,
the Telerik team
Explore the entire Telerik portfolio by downloading the Ultimate Collection trial package. Get it now >>