First, let me establish the system details:
FreePBX 15.0.37.1 on bare metal – Up to date modules
All extensions are PJSIP
All IP Phones are Grandstream GXP2160’s with varying versions of the firmware.
There are seven IP phones in this system, all configured with FreePBX’s EPM - nothing custom about the configuration.
The firmware on the phones does vary. The firmware version on the problematic phones is version Version 1.0.11.71, which I believe is the latest.
The preferred codec is G729
The network is a very vanilla flat 192.168.1.1/24 network with nothing remarkable in place.
The network equipment is a Unifi setup. One USG Pro 4 and a US-24-POE
Now, let me explain the behavior I see. All my inter-office calls work just fine between all the phones except for two of them, which have a one-way audio issue. In the case of these two phones, they cannot hear inbound inter-office audio. The outbound inter-office audio from these two phones is working.
I did turn on verbose PJSIP logging in Asterisk. I also performed a PCAP and reviewed it.
I didn’t see anything remarkable in those logs just yet, though I will be honest I may not know what to look for.
I find this situation rather odd as I’ve got many identical deployments and have never experienced this issue.
I can post whatever logs or PCAPs would be helpful on request. Any input or advice would be much appreciated.