Texture Overlap Issues

Hi, each piece of CAS item from maxis have a specific area assigned for their texture.
You can see what is assigned where from here sims4studio.com/post/192696/thread

You can put your texture anywhere on the template but the best practice is to put it on the specified area, so for skirt & pants you put it on the "bottom" area, shirts on the "top" area & so on. This is done to avoid any overlapping texture issue. If you want to know more you can export out maxis item & see where they put their texture.

Now if you look at the template there is a free space on the lower right of the texture, this is usually where CC creator put their texture if they don't want the texture to overlap with other piece of CAS item from maxis.
Sometimes different CC from different creator use the same area for their texture & that is when you see the texture overlap issue.
For testing, try exporting the diffuse texture from the 2 CC that have overlapping texture issue & you will see that the diffuse is probably overlapping with each other.

To fix this you need to move the texture to a different location where it doesn't occupy the same area with the other CC you want to use.
This involve moving the uv_0 (this is the coordinate that the 3d object uses to know where their texture is) & all the associated texture (diffuse, specular, normal, shadow, etc).
For this you will need Blender to move the uv_0 & any image editing software to move the texture (photopea, gimp, photoshop).

This is a bit old but you might try this tutorial sims4studio.com/post/133947/thread.
And this operation is not specific for the Sims, this is used in general 3D workflow too so you can google something like "moving uv in blender" if you want more.

Hope this helps 😊.