If you notice some weird artifacts regarding the texture of your Sims 4 mesh, make sure that your UV map in Blender is clean. This often happens when creating frankenmeshes. You put multiple assets together, but didn’t notice that there are some small parts of the UV map laying on top of each other.
To fix this, select the part on the UV map and move it to another place (the best practice for this one is to always move the less detailed textured ones to keep a high quality and avoid unneccessary work).
Keep in mind that you have to adjust your texture too, if you moved parts of the UV map. UV map and texture have to match exactly.
There are some use cases where overlaps in the UV map are ok. For example when you need to use a part of the texture multiple times like hairstrands.
Need a visual explanation? Here is the tutorial in a video:
