Domain Mapping- Why are there two versions of my site running; the "" and &q

On my multi install, i have domain mapping on a clients subdomain site. It seems to show two versions of the site when you use and do not use the ‘www’. This issue is here: leads site when i used a ‘coming soon’ plugin. and seems to lead to the correct (current) site.

I have removed the plugins completely from the main multisite and tried various other problem solving testing, however I am stuck .

This is puzzling to me for I have no issue with another clients domain mapping on another subdomain.

Before I go in greater details, just wanted to know if there was any quick fixes I might be missing? thx.