It's a common issue that hasn't been resolved and I haven't seen a response from 343's end in years. Happens to me about half of the time in 4v4 and about 90% of the time in BTB. It makes matchmaking times about triple, assuming it even matches after the other people waiting around don't dashboard quit too. In my experience, it's usually just someone who either dashboard quit because the game throws you back into the playlist, got dropped from their fireteam similar to you, or someone stuck in a hard freeze (another years old issue that I haven't even seen a response to).



Concerning your other issue, are you and your friend playing on the same network? That's always gave my household trouble in H5 but no other game.