@Jip ok, took a while before we could get together to see the issue.
It's probably not the ICE adapter, but it looks like it keeps the game client open behind the 'bad password' message, and if you try to reconnect, it will just stay 'connecting' forever without connecting.
To recreate:
Have someone start a lobby.
purposely join with wrong password.
you will get a bad password message and the FAF client will be on top.
attempt to rejoin the same game with the correct password
You will see 'connecting' but you will not connect, because the first client never closed, but someone who doesn't alt-tab or use task manager will not immediately see that anything is wrong; only the infinite connect window.
Solution is just to close all instances of FA and retry, but it might be what's catching people.