o.k. thanks so far.
so to just understand right: the decribed ‘issue’ is quite ‘normal’ behaviour and the extension code is necessary to make wp itself behave like we want it for cpt’s. in other words… there is nothing ‘wrong’ so far when there is no post-nav shown for custom post types, although they use the standard wp post- and singlepost-templates. right?
or is there still something that should have been done another way?