Hello,
Over the past week I’ve had numerous issues playing co-op with my partner. At various times we have been unable to form a party, unable to chat in party, and unable to start co-op games. I’ve also been randomly kicked from the party after completing a co-op game. At times it also seems like chat messages are being dropped from one side or the other.
My partner re-installed their game once. I have avoided that because it takes several days for me to do so due to slow internet. Constantly reinstalling this game is a bad way to resolve technical issues.