THE MASTER CHIEF COLLECTION LASO BUG

I completed halo 3 Laso playlist with three of my buds and only two outta four unlocked the achievement . It says my buddy and I need to complete the epilouge yet we clearly can’t do that since it starts us from seiraa 117 . But all progress is there.

You might post this here:
https://www.halowaypoint.com/en-us/forums/84ad72a8b51847978545f685f651fc15/topics/achievement-progress-unlock-reports/d3a61929-3917-4224-b723-be59860816e8/posts

Review any YT videos on doing this and making sure you have all requirements to get this achievement.