The root cause is that last year someone started launching DDOS attack against FAF infrastructure. We had to implement significant changes to mitigate them. That's why originally nobody could even log in, after that nobody could see hosted games. We fixed these issues, but the connections during the game are still the weak link if they need to use a relay server, as that one can be overloaded by DDOS.
I suspect that the attacker is targeting your tournaments now, as it seemed to be quiet for a while but today people reported a lot of connection issues.
We tried using a professional provider of ICE relay servers, to improve relayed connections, but I am not sure what the latest status there is. One of the server admins would have to comment on that.
We are all aware that we are losing players over this, but it is not a straightforward fix.