Friends keeps disconnecting from multiplayer

[Mads Trier Braas]

Me and two friends of mine have been enjoying a shared game, with me as host, for a few months now. We usually play 2 or 3 times a month.

Since patch 9, one of my friends keep aggressively disconnecting from the game, usually within 2 minutes.

I tried hosting a new save and it still happens.
Out other friend tried hosting and it still happened.
He tried hosting himself, but then only I could see the lobby, our other friend couldn't.
Up until patch 9, it worked without disconnections - he's had no change in router, computer or ISP.

Any ideas?