Party members being left behind

Jion a party que up for matchmaking with them and some members of the party go into a game some don't. So we all go back to menu try again and again some go into a game some dont. It's not always the same party members left on the menu screen sometimes different just took me and the boys 8 time for us to be able to join a game together after the game we let it que us up for another game and again only some of us got took into the next game others where left on the end game screen and that happens a lot to.