Hi. This issue is not caused by vertex paint but the vertex paint is wrong, yes. In newer versions of Blender the default shading in the viewport in Vertex paint differs from 2.7. Before sampling the color, you need to switch shading to bounding box or just paint skirts with 3fff00, accessories and hair with 007f00, everting else with 00ff00. You can also transfer vertex paint using Data transfer.
The issue is caused by your choice of the item to clone.
s4s is a packaging software that allows you to duplicate, preview and edit game files, it does not create them from scratch. Each meshgroup of the item you clone is affected by specific bones, is tuned to be positioned in a certain way, interact with specific CAS items, and possibly affect the mood.
You cloned a nude lower body and replaced it with a full-body dress.
- nude body parts comes with a buff that can make sims embarrassed when other sims see them wearing the item;
- the lower half does not come with slot rays interactions ( basically arm position ) a full-body should have. Sometimes the games reacts to this with a glitch like
this;
- the lower half is not affected by the bones from the upper body. By importing a full-body item you are introducing new bones. Sometimes the game can react to this with severe distortions like the type you're seeing;
- but the distortion you're seeing is actually caused by skirt bones that the nude lower body did not have. You transferred weights from a dress that was long enough to be affected by skirt bones, so they were transferred to your dress. By replacing the lower nude body with it you introduced new bones. You are lucky to see the distortion in your game because not every creator gets it but people who use their cc do.
Solution: clone yfBody_DressFlutter and import the item there
A few other things:
Never use Make blank button. It can disrupt the structure of the file.
UVs generated in the default square space of MD will stretch when rectangular TS4 textures are applied. You need to select the garment's uvs first and shrink them with S Y 0.5
Thanks, it's working now, will practice some more. <3