The first (bottom) error suggests there are errors in the UV map. Try recreating the UV map.

 <genexpr>
    elem_data_single_int32_array(lay_uv, b"UVIndex", (uv2idx[uv_id] for uv_id in _uvtuples_gen(t_luv, t_lvidx)))
KeyError: ((nan, nan), 43)

The first (bottom) error suggests there are errors in the UV map. Try recreating the UV map. The FBX export module requires a valid UV unwrapping for all vertices in the model. Go into the UV Unwrap tab and re-unwrap your model(s).