Gigaset N300 sends premature SIP BYE

[darcey]

I do not think my issue is with the configuration of FreePBX but hope someone here may have experienced it and can advise.
I have FreePBX set up on my LAN with a single trunk to an external provider (NATted).
Extensions comprise a softphone on my mobile (ext 403) and a Gigaset N300 with two handsets (ext 401 and 402). All are communicating directly over the same network segment with the PBX.
Everything is working well except:
Calls made from the gigaset handset often, but not always, disconnect when the call exceeds 15 minutes. e.g. 15:10, 15:30 etc.
I have captured SIP traffic on both the WAN and the LAN and it is evident my side sends the BYE. What’s more, the BYE originates with the Gigaset N300 base and so Freepbx communicates this to the external provider. So I don’t see the issue resides with the FreePBX instance.
Does anyone have experience of this behaviour? Bearing in mind it is not 100% reproducible but happens about 70% of the time that a call exceeds 15 minutes.

Any ideas greatly appreciated.
Thanks.

[david55]

15 minutes suggests a problem with session timers. Possibly a dynamic rule in your router is timing out.

As a technical point, Asteisk doesn’t forward BYE. The BYE on the other leg is a new BYE, and is not an inevitable consequence of an incoming hangup.

Does the incoming BYE have a reason header? If so what does it contain?

[darcey]

Thanks. The router is OPNsense and I have also used pfSense. Normal vs conservative firewall policies produce no discernible changes.
Some calls to the same number have completed normally and lasted over 1 hour uninterrupted.

Looking at the BYEs associated with a recent disconnect, The BYE from the N300 IP contains no reason header. The BYE, then sent by the PBX to the trunk provider is::

        Reason: Q.850;cause=16
            Reason protocols: Q.850
            Cause: Normal call clearing (16)

Which I am guessing is a ‘normal’ action when an extension has been seen to end the call. I have no way of digging in to the bahaviour of the N300 or linked handsets.