Our group of 4 people (from all over the world as well as a couple in the same network) notice consistent disconnects if the host (whether local or shared save) is running Windows 11. If a Windows 10 player hosts the game, the disconnects stop.
Another connection issue was reconnecting; if a player disconnects for any reason and attempts to rejoin the game, they're met almost instantly with a "Failed to join game" error. We thought this might have something to do with the game insisting to use Xbox Live so we all made sure to add each other as friends on that platform too. That seems to have fixed the issue, it didn't come up again for the rest of our ~3 hour play session tonight.
This happens in literally any combat in multiplayer, even vs harmless, 1-shotable enemies. AND if you log into a game with any Quickness effects, then remove them? Boom, you're permaslowed! It's seriously amazing that this Quickness "upgrade" failed to be tested even to this instantly obvious extent...