URL is not changing from mapped domain to original site so am getting ssl error

we have a site gildas.ucsc.edu and we have domain mapping set to redirect the login and administration to the original domain, gildas.sites.ucsc.edu. It appears to work on firefox but not chrome or safari. However, some people are telling me it works for them on chrome.

Sometimes it seems to work and other times it doesn't.

The problem is that because it's not switching to the original domain, we get an SSL error because we don't have a cert for every alias people need and we can't get a wildcard cert for ucsc.edu

On our dev system, it is similar but not the same: faculty-dev.ucsc.edu/wp-login.php should go to taft.sites-dev.ucsc.edu/wp-login.php and it works on chrome and firefox but not safari.

Any ideas at all?