We have an issue with a couple of peers - when the called party hangs up, they (the peer) does not receive the appropriate BYE message and call appears as still connected at peers end. Then it drops after 30 seconds and sends us BYE.

Current setup is the following:

PEER IP > KAMAILIO 4.2.2 > (Asterisk PBX 1, 2, 3, …, N)

We provision only termination services, which is:

1) peer calls us

2) Kamailio chooses destination using dispatcher module

3) forwards the call to it.

Attached is captured trace.

Clearly BYE is retransmitted a few times, then request for UPDATE is received but it is not possible to answer it because the call is already hung up (as far as I understand).

Kamailio routing file is available upon request.

Thank you in advance!