Cisco Call Manager drops calls after 30 mins

Had an issue recently where calls were dropping after exactly 30 minutes. We did a packet capture on the CUBE router which showed that every 15 minutes both the telco and CUCM were sending re-invites to refresh the session. However the CUBE was not forwarding it on, so the call would disconnect at the session expires timer of 1800 or 30 min. Used the following to fix the issue:

voice service voip

sip

session refresh