Confbridge struct not release when multipleserver confbridge

Asterisk 11.5.1 and Centos 6 module:app_confbridge.c

Issue: How to delete confbridge struct in case of
multiserver Confbridge using IAX2.
NOTE:In single server there is no any such issue ?
void conf_ended(struct conference_bridge *conference_bridge){
ao2_unlink(conference_bridges, conference_bridge);
send_conf_end_event(conference_bridge->name);
conf_stop_record_thread(conference_bridge);

/* say counter= no of activeusers + no of waitingusers */
if(!conference_bridge->counter)
destroy_conference_bridge(conference_bridge);
}
step1: 1st user call on Server A with ConfbridgeNO:1234567
step2: 2nd user call on Server B with ConfbridgeNO:1234567
step 3 : after Join Both to Confbridge NO:1234567
step 4 : After Hangup both hangup

/******* after Join Both to Confbridge NO:1234567 **/
Server A:
Server B
CLI> confbridge list
Conference Bridge Name Users Marked Locked?
================================ ====== ====== ========
1234567 2 2 unlocked
Server B:
Server B
CLI> confbridge list
Conference Bridge Name Users Marked Locked?
================================ ====== ====== ========
1234567 2 2 unlocked

step4 : /** After Hangup both user */
Server B:
Server A
CLI> confbridge list
Server B
CLI> confbridge list
Conference Bridge Name Users Marked Locked?
================================ ====== ====== ========

Server A:
here is issue
Server A*CLI> confbridge list
Conference Bridge Name Users Marked Locked?
================================ ====== ====== ========
1234567 0 0 unlocked