GoogleTalk Firewall Issue

Using googletalk plugin in Iceweasel to make voice calls in standard VirtualBox Whonix setup works fine.
Same plugin in Whonix-Qubes causes calls to drop after 2 mins (exactly).

Usually, the plugin says “Calling…” until connected, then it switches to “In Call…”
But in Whonix-Qubes, it stays on “Calling” for 2 mins and then drops the call because it thinks that no connection was made. Error: “Call failed to connect because the number was unreachable.” However, the call goes through normally and the audio is fine.

I found this regarding GoogleTalk Call Signaling:
but I don’t understand any of it. What is different in Whonix-Qubes vs Standard Whonix that is causing the call signaling to fail?

Part2: probably unrelated but …

I set up tor -> vpn to tunnel udp traffic and tried to get linphone/jitsi to work.
udp is tunneling ok because sign-in works
calls connect but again no rtp stream for audio.
haven’t tested recently but it did work in the past using virtualbox whonix.
something is blocking rtp in whonix-qubes and why should any firewall matter if everything is tunneling through vpn on the workstation?