Can't complete VoIP calls when connected to Roadwarrior VPN

[entree3437]

Hello

I currently run a roadwarrior VPN setup (following this guide) for my phone. On the phone end of things I have only LAN traffic going through the VPN tunnel (shitty upload speed) including DNS since I run Adguard Home on OPNsense. I do also have the outbound NAT rule configured for the wireguard subnet.

Recently I signed up for JMP.chat, which basically is just a VoIP provider. When I try to make a call via JMP while connected to my roadwarrior VPN, it will ring the other person but when they answer it just keeps ringing on my end. Seems like the SIP connection is established but the actual audio feed won't connect? Idk too much about VoIP stuff lol. But anyway, as soon as I disconnect from the VPN, it works perfectly (even still routing through opnsense, which is why I know it's something with the VPN). This is on my Android phone, but I also tested with my Linux laptop and the same issue occurs.

Additionally, I tried a VoIP call via Signal while connected to the VPN and it had the same issue, so I don't think it's a JMP issue. I tried looking in the firewall logs in OPNsense and am not seeing any block logs.

If anyone has any tips for how I can troubleshoot this (tests to run or something), that would be awesome, thanks! And if there's any additional information I can provide please let me know.

P.S. Currently running 23.7 but this issue occurred before upgrading as well.

[samnet]

its been a year and I was wondering if you had any luck fixing this?