Dress Problem with LOD 3

Hi. Every item you clone comes tuned in a specific way. Whatever you replace it with inherits this tuning. To avoid problems like this, you should make your item the same exact way the original is made. You should transfer weights from the original, split it as the original is and replace corresponding parts of the original with yours.
yfBody_DressMaxi_Additions is not affected by b__L_Thigh__ and b__R_Thigh__ bones, yours is. This is them acting up.
Cloning something else that is affected by them will fix this problem but be prepared to encounter other ones because the mesh is not split the same way.

When choosing a reference, go for the one that is of the same type (skirt-like bottom or pants-like bottom), length and has as little sculpted details as possible. Then you can transfer weights, uv_1 and vertex paint from it, and it will behave as intended. Right now the uv_1 is very ripped, the vertex paint is not correct(the skirt will be affected by leg sliders) and the weights do not match the ones in the package.
Also, try to not use decimate, it rips the uvs and ruins topology, making the mesh look like crumpled paper. In MD either change the topology to quads and keep Particle distance high or retopologize the mesh