How high?
Other stuff, make sure that nobody from SHOUT equipment is sending to you, SHOUT equipment is not FRC H323 compliant eventhough they are H323 compatible, it means that they are breaking the gatekeeper consistency table, the gatekeeper founds the table corrupt and erase the complete table making it reload and reset all active calls.
This happens with SHOUT equipment sending to Voicemaster so far.
Let me know if this is your case.
Regards,
Saul F Bejarano