Problem with Hide Backend needing fixed ASAP

So multisite + domain mapping is now working for me with Hide Backend although it has now broke my site for half the visitors…

My url is just http://mysite.com and if the user types http://www.mysite.com it redirects in the normal fashion to http://mysite.com

With hide backend enabled and going to www. it redirects to mysite.com/wp-signup.php?new=www !

https://ww.wp.xz.cn/plugins/better-wp-security/