Call and video-call remain in "Call connecting" state

The call and video-call can't establish and remain in "Call connecting" state

i'm on a custom homeserver ( fairydust.space )

when i'm on **4G** and/or on **VPN**, doesn't work; ❌
but when i'm on **WiFi** without VPN, works ✔

i tried to establish a call between:

- fairydust.space <-> fairydust.space ❌
- fairydust.space <-> matrix.org ❌

also works when i try to use element-desktop, only with the "Peer-to-Peer" option enabled and "turn.matrix.org" disabled

- element-desktop (p2p) <-> element-desktop (p2p) ✔

i tried on the OS:

- Android 10 & 11
- Windows 10

i tried with:

- Element fdroid 1.1.0 & Element fdroid dev 1.1.4 build 1889
- Element-Desktop 1.7.24

i've already made a "rageshake" with the full verbose log, i'm making it another here so i can track the issue