Humanoid changing character texture and avoid removing texture Id

Basically when I add a Humanoid to my character this happens, the video is pretty much self- explanatory:

As you can see, the Upper Torso does have a texture, but the Lower torso doesn’t.

When I add the Humanoid the Upper Torso controls the Lower Torso material and does not let me modify it, this is also happening to all parts in the character, without Humanoid they are customizable, with Humanoid they stick to the texture that the UpperTorso has

Also is happening with normal materials, with no texture or anything

Any clues in what could be happening?
Any help is really appreciated