The most important message from the error log is the last one:
(mmat, amat) = mesh.armature_setup[self]
KeyError: None
Looks as if something is going wrong with the armatures in your FBX and the Blender importer. I am not an expert on FBX nor on armatures. But it looks as if there are already a few tickets on Blender side that mention some limitations:
And there is also some discussion ongoing in here on FBX and Blender im- and export. Although it is mostly for export, maybe there are some helping comments?