The problem is that you have a click action registered on the <a> tag, so clicking on the checkbox will toggle the favourite through it’s own handlers, then the event is propagated up to the parent <a> tag which then toggles it back again.
Obviously this is in the old global-style and would need updating for modern Ember but I hope it illustrates the necessary workaround - replace your {{input type="checkbox"}} component with a similar component that stops the click event from propagating to parent inputs the same as you would with normal jQuery.