The MP Campaign seems to be full of locality errors. i.e What happens on the hosting computer does not necessarily happen on the client computers. Here's a few examples from my last three sessions with a friend. He is playing as the server, I joined him as a client.
1) Cutscenes and sounds only play on host computer.
2) Shots fired by by hosting player cannot be heard nor seen bly client player. The effects (dying and explosions) are shown on all clients however.
3) Client and host can be at the same location, but still unable to see eachother in game. Mostly happens when both players dismounts from a vehicle.
Problem #1 is most likely a script that only runs on one computer. A classic noob mistake. #2 and #3 are clearly not scripting bugs. I've managed to reproduce some of them after extensive testing. They seem to be connected to the MP campaign mode only. It is impossible to create these errors in a normal MP mission. But if you create a user made campaign with the same (fully working) MP-mission included the errors will show up.
Two things seems to trigger these MP/Campaign bugs. Either when the players step out of a vehicle, after travelling cross country; or when a saved game is loaded and a client player joins the campaign.
Anyone else got similar experiences? Please share your thoughts.