Is this still an issue? Im buying an xbox one S just for halo since reach is coming but i dont want to restart my legendary master chief saga on halo 4's 1st mission.
Is there a workaround?
I have not heard new reports of this bug since the first major update last fall, so it is not likely to affect you anymore.
If it does, you should be able to get around to it by starting the mission on Co-op, completing it, and then resuming on Solo for the next several missions.
There is a different but more annoying bug, however. You must play The Maw on Solo, not Co-op, for it to count as completed. The next two missions in the playlist, The Heretic and The Armory, are not Co-op missions and mess up playlist completion progress when going through it on Co-op.
To summarize, you can play every mission of the Master Chief Saga on Co-op until Halo: CE mission The Maw. At this point, you must complete the mission solo and complete The Heretic and The Armory solo as well before resuming Co-op on Halo 2 mission Cairo Station.
Also, I just realized you said Legendary MC Saga. Since it is all of the LASO missions in CE, 2, 3, and 4, I am compiling two saves for that playlist: One at The Maw and another at Epilogue in Halo 4. Hopefully these saves will help people who encounter this issue in the playlist since it is so prevalent.
Either way, I do recommend the game despite this bug, as it is a very rewarding experience to replay the Halo games. I wish you luck with your future MCC endeavors!