2.1.0 tried to make it safe to create the controller twice.
However I still noticed a problem when loading models
in the constructor of MY_Controller (using db auto-connect).
This caused an error "Undefined property: Page_Not_Found::$db"
I wouldn't be surprised if there were other lurking issues.
(E.g. I notice the hooks called "pre_controller" and "post_controller"
... those names could be misleading in the case where the controller
was created twice).
This also happens to affect #1062
(404_override with _remap() method doesn't work).
_remap() should now get invoked whenever the 404_override
is used, instead of only in some cases.