Some of the issues were not reproducible when loading the patch fresh. so it is not completely conclusive, why the original issue appeared.
Yes, you heard it here first, if you are sure that some manual Typing should work, but import or casting errors appear anyway, don't be afraid to restart vvvv and Retype. To my understanding, this forces a fresh build of your vl document.
Of course this should not happen, so more investigation will be necessary.
Mind you, this is an alpha issue, especially issued at NODE17. @gregsn tried to isolate the reproducible cases (with the delegate) after I could explain their mechanisms and made automated tests for that, to be sure that all future development is aware if it ever accidentally changes the expected behaviour.
So I close this thread for now, because a restart fixed the original issue