No or one way audio is almost always caused by no routing of traffic between the endpoints in the call. The RTP stream, aka audio, will flow between the devices that are part of the call, only signaling goes between the device and CM. So signaling traffic successfully passes as the call proceeds. When the call is set on hold the media will be coming from the music on hold server(s), ie from one, or more of the CMs. This works because the devices can communicate with CM. You’re likely problem is that traffic cannot flow between the endspoints that is part of the call.
From the video you shared i can hear MOH audio, when you place the call on Hold MOH will get played from MOH server which can be any one of your CUCM servers and that the reason you see RX packets.
Kindly verify your network routing, one way audio issues are mostly due to network route problems. I assume your network has only permission to reach CUCM servers and other server Like unity and phone subnet are blocked
