having trouble playing co-op campaign

My friend keeps getting a connection lost message when we try an load a mission. Hee checked his connections and all are good. We have had this issue multiple times. It has happened to both of us at one time or another. The 2 times we have been able to play, one of us would be kicked out at a random point in the mission. We don’t know what to do. I read that there were some server issues and that they thought they were fixed but apparently they haven’t been.