Halo 4 terrain not loading - Reclaimer - PC MCC

I’m playing on PC, the game has worked flawlessly until this point:

After defeating the Lich I get to the point where we cross the river and everyone needs to get back on the mammoth. However, the river and all subsequent terrain doesn’t load. I can physically fall down into oblivion if I jump into the void. If I stay in the mammoth everything disappears and I’m stuck in place, if I stand on top of the mammoth I die from what seems like an impact from an unseen object.

Has anyone else encountered this issue, if so how can I fix it? I’ve tried restarting from the last checkpoint, and restarting the pc and quitting mcc (making sure it isn’t still running after I closed it). I haven’t tried uninstalling it yet as I don’t want to lose any progress in any of my other campaigns (will I lose my progress if I uninstall?)

This is currently a known issue OP, you can find more details about it here:
https://support.halowaypoint.com/hc/en-us/articles/360052516151