I havent watched your fbx file (with my i-net it takes a little while to download it ^^), but are those missing parts made out of planes? When yes make the “solid” or enable “two sided” in the material
Thanks . They are not planes, just thin polygons. I originally thought it was a reversed normals problem but the spikes show up when importing as a static mesh. Importing as a skeletal mesh, as I need to, seems to make them disappear.