I get polygon explosions when I delete segments from Mizu's waist model (ch03_066_0015)

[habunatinongara]

I can't remove the underskirt of Mizu's waist model without polygon explosions.

When I remove the segments "Group_0_Sub_1__shellfer_UseSC" and "Group_0_Sub_2__ch03_066_0010_hair_UseSC" from the mesh, the result in game are always those polygon explosions. I tried to remove the vertex groups "X_side_01_cloth_HJ_00_GCJ_00X" from the skirt and deleted the according bones from the armature and the nodes in the .chain-file, but it doesn't seem to change anything at all.

Can somebody give me an explanation why this error appears?

If more information is needed, just let me know.

Thanks in advance.