Hi there! Is this a VoIP or a VideoConference meeting? Wich technology? (ie: Avaya Aura CM, Cisco CUCM).
I remember how the session helper made some strange beahavior too.
Like this one:
show system session-helper
set name sip
set protocol 17
set port 5060
Just for tring something, you could do a backup for the session helper, remove them and try again.