So me and a friend were both having the issue, but we had game mode enabled already
without luck. The weird thing is all the levels in Halo:CEA up until The Maw worked fine. But then the "Connection Interrupted" issue on The Maw.
We tried everything to no avail:
- Enabling UPNP
- Port Forwarding Manually
- Enabling / Disabling relays
- Disabling all irrelevant background processes
- Disabling Game Mode
- Pre-caching the game in Singleplayer
- Throttling potentially faster HDD on one player's system and CPIU with a benchmark test (lol)
Although... Player A had no problems with playing "The Maw" with other players (We'll call "Player C"), so we knew something was up with "Player B". Finally, we got the following to work:
- Player B moved installation to a faster hard-drive (C drive)
- Player B opened a game with Player C to "pre-cache" the mission files(?)
- Player B left game with Player C
- Player A invited Player B back
- Game launched without issue.
: Player B potentially had a slower hard drive than Player A. Player B moved games to a faster alternative harddrive.