Whoever enveloped those models didn't hide the bone_root/pelvis correctly and it's frozen and visible at the base of the model. You can re-envelop the models or you can simply find some other model to use.

I've had the same problem with the original AT-RT driver and Commander Cody models but I'm now using different models. I don't know much about hex-editing the models except for adding addons to the model and changing textures, so I'm sorry I cannot be of more help. You could try putting a request in the SWBF2 All-Purpose Request Thread.