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vronski: When I join the multiplayer game with my priest the game crashes either in loading screen or in town after a few seconds.

edit: It crashes even if I host it.
fogWraith: The dummies also relocate themselves at random and place themselves inside the fountain, the error log is riddled with Couldn't find message type 65535!.

Crashes here as well, the v79 patch is broken on GOG, but appears to work just fine on Steam.
What about version 80, does that crash for you?