Error when starting PS and PC players simultaneously in a party

I'm having the same issue.  When I am party leader I get that message when I try to start matchmaking.  When my buddy is party leader he doesn't get the message and can match into a game, however I remain stuck in the main menu while he joins a game.  I have to leave the party and then re-join his party after he's started a match to then be able to play with him, usually I am put into a queue first.