While I’ve come to learn that this is an issue with the game itself, this happens in The Silent Cartographer on your mod especially. Every time on Legendary, there’s only one guy that has a unique face variation while every other marine has Stacker’s face (Not the ODSTs and the Sergeant for obvious reasons). I never noticed something like this happening anywhere else either. If there’s one or two guys that has that face and is not a Sergeant, that’s not out of the ordinary - but everyone aside from the one guy looking like Stacker is just really odd. I’ve heard this is a common issue for HCE and Dervish proposed a technical fix from Galap of the Halo Modding Reclaimers in #halo-discussion on your Discord, so it might be amenable.