Sometimes caller and callee can't hear each other

Hello. I’m trying to fix an issue we have in our office phone. On a regular basis, the caller doesn’t hear the callee or viceversa.

We tried several times until this issue was reproduced and we were able to record the details of the call (picture attached). We ran the command “tcpdump -s 0 -i any -w sip-trace.pcap” to obtain this information. The caller is 787-431-2415 and the callee is 813-879-6800. The callee transferred the call to extension 316. At this point the person at extension 316 could hear the caller, but the caller (787-431-2415) couldn’t hear the callee.

Thank you.