I have a small FreePBX installation with 6 phones. I am baffled by a seemingly random issue where sometimes when someone answers a phone to take an incoming call from an external caller, the person answering the phone hears the hold music instead of the caller. It never happens when calling between extensions. It is fairly uncommon (maybe 1 or 2 per day out of 20 or so).
The phones are Ubiquiti UVP phones, and our trunk provider uses a session border controller inserted directly into the LAN. Five of the phones are in a single ring group that rings all the phones at once.
I have a log of one such call taken from the “full” log in FreePBX but since I am a new user in the forum I cannot post a link to it, plus it is ~400 lines, so it would be annoying to everyone to dump it here. The only things that stand out to me in the log are these entries right next to each other:
bridge_channel.c: Channel SIP/5-00000120 joined 'simple_bridge' basic-bridge bridge_channel.c: Channel SIP/TrunkName-0000011c joined 'simple_bridge' basic-bridge res_musiconhold.c: Started music on hold, class 'default', on channel 'SIP/5-00000120'
I have been trying to figure out why this is happening for quite some time and would appreciate any insight somebody might have. I’d be happy to provide more information if needed.
Some things I have tried include disabling hold music (users just hear silence when answered instead of music) and switching to Asterisk 15 instead of 13 (I had read somewhere that 13 might have been the issue).