Controllers must not be of scope singleton
Currently all the controllers of Flow (and the ones that you create via the kickstarter) are of scope singleton (e.g. contain the @Flow\Scope("singleton") annotation).
Usually that doesn't really make a difference, because controllers are only instantiated once.
But if we start using the same controller multiple times (say two plugin instances on one page) we'll get really weird effects..
BTW: For command controllers it's obviously OK to be singletons, but there is no advantage in doing so