Co-op Connection Failed When I'm Host?!

Several times now I have been trying to play co-op with a friend and even though I am the host I lose connection?! It shows the loading screen for the level, then goes to the blue planet background loading screen, then kicks back to main menu says connection lost to the game session? This nonsense is ridiculous. I will not be buying Halo 5. I think we should be given it for free at this point because this is just absurd how many issues there are a month later.

After some testing (more than 343 has done, apparently), I found we can start the level fine with no skulls on. But, turn on Prophet Birthday Party, to go for that achievement, and it fails. Seriously, give us some notification on all these problems 343! There are way more issues than just matchmaking yet that is all the patches have attempted to fix? Or is that admission of guilt or something?!

I’m experiencing a problem where my friends and I can’t even play together. We can get into the same party, but when we go into the game it divides us up and says we can’t be together because we aren’t co.nnected to the game. I wanna play co-op but just won’t let us join each other. Our connections and everything is fine cause we can get into multiplayer, but the game just won’t let us be together.