Maybe its too late for me and I do anything wrong but cant find any solution for this:

http://ift.tt/1vAxFlO


When you remove responsiveConfig and use activeItem only, everything is fine. However when you use responsiveConfig, you will get error: Cannot read property 'length' of undefined


One more thing in fiddle - when I change Container to Viewport (which extends from Container) I get following error: Uncaught Error: Config "fn" has no setter on class Ext.container.Viewport


Still hope this won't be necessary when you add dynamic layout switching.