How come the entire model doesn't follow the ragdoll/rig?

I have a fully animated (humanoid) character. When they die I am activating their ragdoll. But not all objects of the mesh follow the ragdoll. I’m just using the default ragdoll wizard to create it. Any ideas as to why this is?

Here’s what it looks like:

The rig is made in Blender using Rigify, if that helps or has any known problems with it. I have 1 enemy that it works with but 2 that do the above (all using the same bones in the creation wizard)

This is what it normally looks like.

The meshes on the left are meshes that don’t move once the ragdoll is activate (left arm, right shoulder, mid-rif). But on the other enemy it’s only on the legs. The right is the crumpled ragdoll (acting the way it should)

Bump (apologies if this bump is too early, I’m not sure what the time between is)