...This modification can involve changing addresses or ports, adding a media stream, deleting a media stream, and so on. This is accomplished by sending a new INVITE request within the same dialog that established the session. An INVITE request sent within an existing dialog is known as a re-INVITE.

Note that a single re-INVITE can modify the dialog and the parameters of the session at the same time.

re-INVITE caused a lot of trouble if we don't know exactly what's going on with UAC/UAS at the time re-INVITE happen.

Asterisk configuration

Instead of reinvite, UPDATE should be used when possibile to avoid any confusion:

UPDATE allows a client to update parameters of a session (such as the set of media streams and their codecs) but has no impact on the state of a dialog. In that sense, it is like a re-INVITE, but unlike re-INVITE, it can be sent before the initial INVITE has been completed. This makes it very useful for updating session parameters within early dialogs.

SIP UPDATE RFC