Kicked from server when starting guild war?

Hi there,
Me and three friends have a small guild and just for trying it out we started a random guild war. We tried three times yesterday but every time this happens:

> all are together in the territory
> we start the war
> countdown reaches 0
> one person (seemingly random) gets sent to some NA server to the tower
> the other three get kicked from the server

We are all EU players, if that has anything to do with it.

Is this a bug or are we missing something obvious here?