I don't know if any or how many players on WGT ever play Urban Terror but if you do you will notice there are some exact similarities to how the games play at times.
If you take notice of them you'll see that it's simply a symptom of using the same type of MP infrastructure.
Everything from lag to 999/disconnects. It's not your computer, and it's not your connection (well most of the time) It's the game and sheer number of accounts active and connecting.
There isn't really much they can do from what I can see, tweaking code to handle network and routing differently really won't do much unless they invest huge amounts of money into hardware and bandwidth.
I know no one wants to acknowledge it but cheat engine is being used, probably by more and more players. Using a program to interfere with and manipulate data which is sent back and forth to the server via your client when playing is gonna cause issues like you're seeing now. The more people doing it, the more issues.
Anyone ever play CS Source when you had players on using lag switches? Brutal at times.
Cheats or Hax will nail the connection to servers in games using this model. It's not hard to figure it out.
Not to say that in your foursome in AS someone is cheating, it's saying that connected to the various servers which are used there are probably cheaters playing in combination with the sheer numbers of players these days on at once it just creates a bad playing environment.