Domain mapped subdomains using 302 redirect....

For some reason our sub-domains are mapped via 302 redirect as opposed to a 301 on two of our MU installs using the domain mapping plugin. It looks like the plugin is intended to use 301 by looking in it and seems to be verified here: https://premium.wpmudev.org/blog/wpmu-domain-mapping-update/

Any ideas on what might be causing the 302 , seems odd as plugin doesn't even have any mentions of 302 redirects.... We are using Version: 2.1.1 of the plugin and 2.9.2 ....