its an annoying problem introduced with the most recent patch, I have had it happen to me a few times.
it occurs when a player times out to some people in the match, but not everyone. the game no longer continues until the person who has lost connection leaves the game, usually by alt tabbing or powering off pc because concede / exit doesn't work.
many people however are reluctant to leave, so it turns into "whoever keeps their computer on all night wins" if you desire.
