>>2864504I didn't try the proposed solutions, because manually fixing the UV map is way more hassle than my current workaround.
And sorry, when I enable wireframe my MMD screen just goes black. Never bothered trying to fix that since I never use wireframes in MMD anyway. Here it is in pmxe though if that helps.
The dress is here:
https://tstorage.info/1dxa21jgsfvaThe material is just standard ray material_cloth.fx