Calls to a FreePBX server dropped after a multiple of 15 minutes (plus ~32 seconds)

[WeirdProbl3m]

Two of us are currently having problems with calls sometimes being dropped after a multiple of 15 minutes (15, 30 or so) by our FreePBX phone system. Calls arrive via SIP from AQL, but only calls from Vodafone numbers are ever lost (I can see the logs on the server).

The logs show something like this:

[2021-08-03 13:58:54] WARNING[1840] chan_sip.c: Retransmission timeout reached on transmission 136351197_117226148@141.170.24.20 for seqno 102 (Critical Request) -- See https://wiki.asterisk.org/wiki/display/AST/SIP+Retransmissions
Packet timed out after 31999ms with no response
[2021-08-03 13:58:54] WARNING[1840] chan_sip.c: Hanging up call 136351197_117226148@141.170.24.20 - no reply to our critical packet (see https://wiki.asterisk.org/wiki/display/AST/SIP+Retransmissions).
[2021-08-03 13:58:54] VERBOSE[22533][C-00024e7d] bridge_channel.c: Channel SIP/141.170.24.20-0000392e left 'softmix' base-bridge <a96e852c-de87-433f-9514-2e4069c60092>
[2021-08-03 13:58:54] VERBOSE[23328][C-00024e7d] bridge_channel.c: Channel CBAnn/987-00023ac6;2 joined 'softmix' base-bridge <a96e852c-de87-433f-9514-2e4069c60092>
[2021-08-03 13:58:54] VERBOSE[22533][C-00024e7d] file.c: <CBAnn/987-00023ac6;1> Playing 'confbridge-leave.gsm' (language 'en')
[2021-08-03 13:58:55] VERBOSE[23328][C-00024e7d] bridge_channel.c: Channel CBAnn/987-00023ac6;2 left 'softmix' base-bridge <a96e852c-de87-433f-9514-2e4069c60092>
[2021-08-03 13:58:55] VERBOSE[22533][C-00024e7d] pbx.c: Executing [h@ext-meetme:1] Macro("SIP/141.170.24.20-0000392e", "hangupcall,") in new stack
[2021-08-03 13:58:55] VERBOSE[22533][C-00024e7d] pbx.c: Executing [s@macro-hangupcall:1] GotoIf("SIP/141.170.24.20-0000392e", "1?theend") in new stack

I called from an iPhone and that didn't immediately realise the call had dropped.

Has anyone seen this before?

[Andy]

Hi @WeirdProbl3m 👋 Can I please check if you have contacted the providers of the FreePBX server to see if they are able to shed any light on where the issue lies? Also does this happen on every call received from a Vodafone number, and have you been able to test this with calls from other networks to make sure it`s only Vodafone calls when this issue occurs? 😊

[WeirdProbl3m]

Hi Andy,

Thank-you for responding. My colleague built the FreePBX server but is away on long term leave. I haven't contacted the SIP trunk provider as yet but will do to see what they say.

No, this doesn't occur on all calls from Vodafone numbers: in fact it's probably only occurring less than five times per week. It's not a high traffic phone system but that's still a small proportion of the calls. Looking through the detailed logs (these are retained for seven days so I cannot go far back), I've never seen this happen with calls from anyone else (mobile or landline): it's only occurring with my personal number (which I'm using for testing) and my colleague's phone (she works from home so it's impacting her more as she doesn't have access to another phone).

Kind Regards

[Evie]

Let us know how you get on with contacting them @WeirdProbl3m 

Just to clarify, you've only noticed the issue on your mobile number and your colleagues mobile number when they call through to your FreeFBX phone? Do you know if this only happens when you're calling from certain locations? 

If you have Wi-Fi calling active on your mobile and you're in an area where the connection can jump between Wi-Fi and mobile data this could be causing the drops.