Co-op is completely broken

Sometimes when I try to play co-op with a friend, the level seems to load but when the loading bar on the loading screen is filled, we get kicked back to the menu. It only happens on co op not singleplayer. This seems to only happen with CE, not Reach, and most of the time all of the other levels load except for the one we are trying to do, but other times all of the levels don’t load. It doesn’t matter who hosts the game, it crashes to menu anyways. When we play through the previous level and get to the next level, it also kicks us back to the menu before we can get to the next level. We tried resetting our games, routers, and computers, but it doesnt work. Usually waiting a full day works, but we are trying to play The Maw and for the past few days it simply doesnt load up. It just gets worse every time we try to play more. Does anyone know how to fix it?