If I understand correctly, because you didn’t specify caller nor callee, you are trying to call from 15452 to 15453 and the call is completely failing so this call doesn’t go through at all, this is not a “one-way audio” issue, rather a networking issue, as FreePBX is not getting any replies back from 15453, as you can see from the multiple re-sends and then the following error message
2018-03-28 09:53:57] WARNING[2531]: chan_sip.c:4169 retrans_pkt: Retransmission timeout reached on transmission 1746742158-25646-4@BA.I.A.J for seqno 31 (Critical Response) – See https://wiki.asterisk.org/wiki/display/AST/SIP+Retransmissions
Packet timed out after 6400ms with no response
[2018-03-28 09:53:57] WARNING[2531]: chan_sip.c:4198 retrans_pkt: Hanging up call 1746742158-25646-4@BA.I.A.J - no reply to our critical packet (see https://wiki.asterisk.org/wiki/display/AST/SIP+Retransmissions).
You need to recheck your network configuration from point to point, also make sure you entered the 3 networks in SIP settings as local networks, and also verify the firewall module configuration on FreePBX if you have enabled it.
My quick guess is that since OpenVPN is not aware of network 192.168.54.x and you probably didn’t specify it as a reachable network on the client configuration file, the endpoint using OpenVPN client doesn’t know how to reach that network, and that is why you are seeing this behaviour.