Redirect Loop when logged into admin and Slow site: domainmap-setup-cdsso

When I log into my network admin, and then I try to the mapped domain, I have a redirect loop. Additionally, the script:
appears on the mapped domain and takes a while to load - it seems to be slowing down my site.
The mapped domain is:

I'm fairly certain that the admin-ajax.php?action=domainmap-setup-cdsso script is causing the redirect (I believe I see the domainmap-setup-cdsso query parameter in the url when it is redirecting).

How do I resolve these two issues (which I believe to be related)?