Okay, found the solution for this as well. We have a cached value here, so we need to change in qa-db-post-create.php:
qa_db_query_sub("REPLACE ^options (title, content) SELECT 'cache_unupaqcount', COUNT(*) FROM ^posts WHERE type='Q' AND amaxvote=0 AND closedbyid IS NULL");
to:
qa_db_query_sub("REPLACE ^options (title, content) SELECT 'cache_unupaqcount', COUNT(*) FROM ^posts WHERE type='Q' AND amaxvote=0 AND closedbyid IS NULL AND acount=0");
Adding a "AND acount=0" in the end.
Afterwards go to /admin/stats and hit the button "recount posts". That's it .)