User creations - not assigned to a user group

Good evening,
The site we are working on at present, we are getting a large number of signups... great
The issue we are having is 70% of them are being directed to the default 'Registered' usergroup, we want them added to a 'Site Members' usergroup.

We have done this to help us flag when and where a user is being created and added into the wrong user group.

Currently we are using the following settings;
User Options
Allow User Registration:- Yes
New User Registration Group :- Site Members
Guest User Group:- Guest
Send Password:- Yes
New User Account Activation:- Self
Notification Mail to Administrators:- Yes
Captcha:- Use Default
Frontend User Parameters:- Show
Frontend Language:- Hide
Change Login Name:- Yes

CB Registration Config
Allow User Registration:- Same as CMS 'allow registration'
Generate Registration Passwords:- No
Admin Approval:- Yes
Email Confirmation:- Yes
Ajax Username Checker:- Yes
Show Login form next to Registration form:- Yes

Where else would i need to check why people are getting directed to the wrong user group on signup?

That's the only parameter core CB uses for registration usergroup. If you're using CB Connect it also has such a parameter, but defaults to whatever CB is using. CBSubs can also assign usergroups, but does not do so by default. Then CB Auto Actions can be configured to assign usergroups, but again does not do so by default. If still doing it after checking all of those then it could be a 3rd party Joomla user plugin within Extensions > Plugins doing it as some extensions have synchronization plugins.

We have added a user sign up menu item to test if this directs them to the correct menu as from what we can see they all have been configured in the locations you mentioned already.

Please PM backend super administrator login credentials and will take a look.

Registration tests through CB worked perfectly fine. I've disabled Joomla registration to prevent possible backdoor registrations. CB is already set to be independent of Joomla. My guess is somehow users were registering directly through Joomla somewhere. Please keep an eye on things and see if the issue persists.