[solved] Mesh glitch in CAS and game

Hi. As Nouchcka said, this is a weight related issue but of a bit different nature.
Whatever you import in the package should have the same vertex groups as the original that is being replaced.
Your garment is affected by foot and toe vertex groups while the item you cloned to start a package is not.
To my knowledge, there is no base game maxis item that has these vertex groups but is made of one meshgroup. The best solution would be to split the mesh the way it should be split and import it in the package started from the original garment you cloned to edit. Keep in mind that each meshgroup should have the same vertex group as a corresponding one that will be replaced, so the fastest way of removing unwanted ones would be with this addon ( just type 0 and click on purchase, it's free). Sometimes meshes have some random vertex groups in the list that have no influence on anything, I do not know if not having them will affect anything ( these distortions do not happen for everyone), but it's best to be safe than to have people tell you your garment distorts. Make sure to compare the list and add some of them
Another thing, never use Make blank feature, it does not actually make maps blank, it just removes them.
Import these maps instead ( while we're at it, you should always import a shadow map in dds, there is some new (?) issue that causes black lines to appear along the borders if the map is imported in png)
New blend and package files, please check how the mesh is split and what vertex groups its meshgroups have

This issue does not appear always and for anyone. However, if you do not see it in your game, someone else using the same cc of yours might see in their.
I do not know what exactly is behind it ( as in what factor determines how the game will display it for me and someone else), unfortunately, but at least we know a solution.

About that spec in the back, interesting thing you found. Look at three gowns before it in the list and you'll see the same thing. Then hover over this area with a cursor and tadam! It does not highlight, the whole bottom row of faces! Maxis 0 : 1 you. The uvs in the uv_1 map are too low. Select the 0 meshgroup, switch to its uv_1 map, select all vertices but the top row, press S Y 0,3 ( just to be safe), then G Y 6.5. Save, re-import, check if it highlights. If not fully, raise a bit more.

About shadow maps, probably not. I do not see these lines on my old meshes and no one reported seeing them, so I assume, unlike those weight related distortions, this is something that happens to anyone and if you are not seeing it, no one else is

- I make sure that my lod0 has very good topology (I now prefer to retopologize manually);
-I open lod1 file exported from the package, append the mesh from lod0 file, MARK ALL SPLIT EDGES AS SHARP ( Select everything with A, Select - Select boundary loop, Shading/UVs tab - Edges - Sharp, this will make it easier to select them later);
- then REMOVE DOUBLES with Merge distance set to 0,0001. This is the reason you get holes, Decimate modifier retopologizes every separate plane individually);
- then I select unnecessary edge loops and either delete them or merge them (Alt M menu, don't forger to enable "UVs" so that they get merged, too). Basically I remove all minor details and extra definition but preserve overall shape. You will have a hard time doing it on a maxis mesh since it is already truangulated and quadrangulation does not give good results. I fell like it would be easier to just frankenmesh lod1 meshes, too;
- once done, I select one sharp edge (they are blue), then Select - Select Similar - Sharpness, then Mesh- Edges - Edge split

So, again, to avoid those holes, removed doubles first. To have an easier time splitting them again, mark them as sharp first