Thanx for trying to solve it ... I got a solution.
1. Nginx works straight forward, but it have default values for "error_page".
Default for the 40x errors are not "none" (like in the docu) it's of course
an internal error page like
error_page 401 403 404 /40x.html
location /40x.html { internal; }
Default for the 50x errors are "none" - means do nothing, pass it through.
2. Like the "access_log" command, it is possible to use more than on.
So the usage of "error_page" in eg. "server" not only overrides one setting in "http",
it wipes it completly out. Everything is set to "none".
So you only have to use one dummy "error_page" command or somthing like (1.)
T.