Alcatel Unleashed

I have an OXO PBX with version 6.x and Fanvil brand SIP phones have been installed, after a while the message timeout appears on all the Fanvil SIP phones, what you have to do is reset the OXO PBX so that the SIP phones register again, please support me with this issue as it is causing problems for users.

That's very vague. We also use Fanvils and we don't see that happening.
Whats the fanvil model? ethernet of wireless models? any wireshark traces from the oxo? any logs from the fanvil?