Since the last update there’s a bug at the time you want to pick up a SMG on halo 3, when you are in front of one and tries to pick it up instead seen the typical SMG model you see the Magnum model.
Gotta check that out… Never happened to me before since the new update.
Please make sure and file bug reports in the Halo Support site about these issues: https://aka.ms/HaloSupport