[SR-Users] NAT Problem! Not relay ACK,CANCEL and BYE to other UA

Hi All, I have 2 interfaces - External A (behind NAT) and Internal B (LAN) in Kamailio Load Balance, and enable Multi-Homing function "mhomed=1". Load Balance dispatches to Kamailio SIP Servers via the Internal B (LAN) (each Kamailio SIP server has both proxy and registrar in one box). For RTP relay, I use RTPproxy in other server, has 2 interfaces A&B like Load Balance. If using 2 interfaces in Load Balance, Registration and calling NORMAL with 2 users behind NAT, but the call will be interrupted after 30 seconds due to the ACK message (after Ringing, 200 OK) STOP in Load Balance in return and not relayed to other UA . CANCEL and BYE have same error like ACK. I tried using only one interface for load balancing (External = Internal IP), and SIP Server binds to Load Balance in the same network, EVERYTHING IS OK. ACK, CANCEL and BYE are not missing behind NAT. For NAT Traversal I use PATH Module in Load Balance, and add "Received" like this: ... modparam("path", "use_received", 1) .. .. record_route(); add_path_received(); force_rport(); t_relay; .. .. And in SIP Server enable Path Parameter for Registrar: modparam("registrar", "use_path", 1) modparam("registrar", "path_mode", 1) modparam("registrar", "path_use_received", 1) Enable "#!define WITH_NAT" in default kamailio.cfg for RTP Controlling, but I removed all fix_nated_register and fix_nated_contact in SIP Server, because using PATH module.I try enable both fix_nat_register and fix_nated_contact, or only fix_nat_register but NOT SOLVE Problem "missing ACK,CANCEL, and BYE in Load Balance" behind NAT. Best Regard, Tuan.