I think I have a work-around but unsure if this a true fix.
If you just add a site and don’t edit several of the site settings you get just the re-direction. You must change the site URL and the HOME to be the full url of the domain you want the sites to be mapped to. Do this manually as the auto update functions, changing the domain url and using the checkbox update site url and home, seems to do weird things.
Madman2