s2s connections breaking after some time/getting timed out?

I have recently started my own server, and I guess it's having some bad time handling s2s connections.

Let's say I just started ejabberd - everything works well for some time, then I notice that some people's statuses doesn't match on my other account (I have 2 jabber accounts configured in my client, one on my own server and the other is remote). This is when I try to relog - and it usually ends up with the contacts from this one server going offline, while the other servers' connections are still alive and working. After some time the connection gets restored, to eventually break again.

This happens to every s2s connection to external server, with a seemingly random pattern. Sometimes all connections work, sometimes just one goes down, sometimes they all go down at once.

The server runs behind a router set up to forward ports in range 2000-8000 to it, I've also set FIREWALL_WINDOW=2000-8000 in /etc/default/ejabberd.

Im using ejabberd 2.1.10 running on Debian 7.3.

Is there anything I might've overlooked in the config file, or maybe the firewall window should be wider? I have no clue at this point. Any help greatly appreciated.

Thanks in advance

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