Mesh Objects not appearing/ are malfunctioning during Animation Sequences

I created an enemy character via Blender, however the animations do not seem to include some of the meshes, yet they are linked to the bones with weight painting. When imported these mesh parts are not visible in the animations and in some animations the meshes are out of place.

The animations in Blender show them appropriately

As you can see the “box plates” of the mesh are in a different place, for some reason, and in other animations are just generally not visible or present at all.