Trying to convert Legion edited models to LK

[Notoriously_Bad]

So I've been trying to convert an edited model from Legion to Lich King, but I'm running into issues. Whenever I put the m2 through a cata+ -> lk converter, parts of the model disappear, specifically right now its the legs. I'm relatively new to model editing and am trying to figure out what causes this to happen. Any help is appreciated.

Here is the model viewer image of the converted model. As can be seen, the legs are missing. Here is the same model in blender, clearly some of the data is still there, but the mesh has disappeared.

I'm focusing on the invisible parts of the model right now, but if anyone can help with the mismapped textures or offset helm position, that would also be greatly appreciated.