[Asterisk-Users] Dropped calls

[Thilo Salmon]

> Ok, I'll watch for that as well since I upgraded my desk's Grandstream to 
> 1.0.4.54 an hour ago (previously I had either 4.26 or 4.17).

It appears the hangup is triggered by a SIP ACK with CSeq set to 0.
Some Grandstream UAs happen to pick 0 as CSeq. chan_sip.c contains

if (!p->lastinvite && !strlen(p->randdata))
                        p->needdestroy = 1;

where p->lastinvite hold the matching CSeq from the last INVITE.
0 in this case...

Fixing this does bring downs the number of hangups, but does not 
entirely solve the problem. We are still looking.

Thilo