Before opening a lobby in system link, get to the ENLISTED PLAYERS menu in splitscreen. This will fix the dirty disk error.
Don't skip the cutscene, it softlocks the game for anyone who isn't the host, and if the hosts skips the cutscene the game hard crashes.
Don't run into loadzones without huddling together first, if two players are between two bsp changes then you will desync.
If all of the players die and the cutscene reverts, the screen will be frozen for anyone who isn't the host.
4 player is finicky with respawns, so try to keep yourself alive.