Ok in 4.95 they fixed my issue as follows:

When Registrar Address was set, the Proxy Domain Name was not used as the host of REGISTER.

I had this a lot in 4.82, it didn't exist in 4.75

4.99 is out in the US I believe, though there is nothing mentioned in the release notes about it.

Also check the alarm logs as from 4.75 and up you get sip error codes which tell you why the registration is failing.