Certain Aastra 480i Intercom/Paging works

I’m trying to setup the Paging and Intercom function with 9133i and 480i Aastra phones.

All the 9133i phones have the capability of starting an Intercom or page with 480i and 9133i phones (Auto answers with a beep noise). Only selective 480i phones are capable of paging and starting an Intercom with 480i and 9133i phones.

The strange thing I been scratching my head for awhile now is that a few 480i phones can only page/intercom with another 480i that will auto answer. If I tried paging/intercom a 9133i phone, it would ring once and reply back with a busy signal.

All the phones are updated with firmware and my Asterisk build is I downgrade the firmware, modified the extension_additional.conf, compare Aastra config files, and examined the asterisk logs when the intercom was in place. In the end I’m stumped.