Local Multiplayer not working

[goeroeg]

We have a very strange problem here, when trying to start a multiplayer game in a local Wi-Fi network. We all have no mods - just a fresh install and starting with an empty world. The hosted game is visible in the list and correctly displayed as "local" - the house symbol instead of the globe.

But when trying to connect it stops when synching at 99% and disconnects. (10% when viewing on the host)

No errors in the log.txt, neither on client nor on server side. Only "player joined" and "player left" entries on the server.

Everything is fine (mostly) when joining an online game, so it seems to be something on the server/host side?

Any ideas somebody? We would appreciate any help, as could not find anything helpful online yet.

[Antaiir]

Check, if the network ports for this game are open/forwarded for the host.

[goeroeg]

Well, sort of - I have the ports open for IPv6, but as I have a DSLite connection, IPv4 is not possible - I hope that should not be an issue.
And as said, the P2P-connection between server and the hosts should be local, what the game correctly indicates.
With other games this works usually by directly entering the IP address of the server - is there a way to do that in FS22 (config file, command line, ...) ?