So I've been having an issue where slowly all my Adult Females' thumbnails and body when using gussy up or plan outfit are showing as pitch black. This hasn't affected my male or other aged sims (teen, elder), and I've noticed my townie AF are fine too. It started with Mary-Sue, who I gave a 4t2 business suit, which showed black in the thumbnail but appeared fine in-game, however her portrait on the left in live-mode shows the black patches:
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From there it has affected my other played females, such as Dina Goth and Cassandra, who aren't wearing any CC:
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I have gone in and changed Mary-Sue's outfit to a different CC dress, which initially didn't have the black patches on the preview, but now does (in fact all my outfits, CC and in-game ones for AF now have the pitch black body from the neck down, the CC dresses shown here were fine yesterday
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It still doesn't show on the in-game model, but my affected sims like Dina have nothing to change into to try fix their portraits because she's in maternity wear, and as you can see her outfits are normal maxis ones.
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I get this is probably a broken CC issue, but even the dress previews where I downloaded it doesn't have the black patches on their preview, and it has since spread to all outfits. Is there a way to clean them or portraits? Also, it looks like the affected AF are wearing necklaces like it could be a necklace that borked their skin, but none of them are actually wearing any

PS: Sorry if this has been asked before, I did search for a previous thread but all my combinations brought me to issues with black box shadows under sims instead

Looks like you have a clothing item or skin that's overlaying AF clothes and/or skin. You might want to sort through your downloads to find the problem CC item.

I think maybe the problem could be those first outfits in the "Buy clothing" picture. They look like they're lacking a skin group for the arms and legs (I'm not sure, though). See if the problem goes away if you remove those from your downloads folder.

If the clothes are the problem, I think the issue should go away once you remove the broken clothes.

If those outfits turn out to be the problem, can you maybe post a link to where you found them? I can take a look to see if there's something going on with the files.

See initially those first pieces of clothing were displaying fine, until I put this dress here onto Mary-Sue as her everyday wear. From then on, loads of files that were appearing fine got those black patches or invisible limbs like the buy clothing picture, including the base game/eaxis packs clothes after I took all CC out
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After that, I decided to repair my game (I am using Ultimate Collection in Origin), which removed most of the black patches from the clothes apart from the ones my affected sims were wearing (Dina/Mary-Sue/Cassandras Formal/Sleepwear/Swim etc), so then I deleted the thumbnail file for CAS and only after that did the clothes appear as normal. I put my CC back in bar the business suit dress I linked and the clothes are appearing normal as they did before:
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I'm unsure if the dress I linked is specifically the problem as I think I need to play with it a bit more and see if the problem pops up again, but it was the only dress that had black patches in the thumbnail immediately after downloading, and it was only after I equipped it that the problem spread.

The dress itself for the recolors has a "wrong" setting because otherwise you risk them overlaying the skin, but in the case of this exact outfit I'm unsure if it matters. Could be a good idea to change it just in case, but the outfits do seem like they work, judging from MDP's pictures.

If you want to see if fixing it helps, in SimPE the "dress" TXMTs in the "cMaterialDefinition" tab should say "SimStandardMaterial" and not "SimSkin" (the "Body" TXMTs are fine, don't touch those). Commit changes and save. (I don't know if MDP would prefer to update the files themselves? Not sure if they have a username here)

Technically this shouldn't affect other outfits than just these recolors (and/or other unfixed recolors), but I'm guessing one of the other settings could be affecting it (not something I'm spotting at first glance, but I have seen some outfits and hairs do this so not ruling it out - a long time ago I tried manually binning a hair (first try) and ended up putting black scalps on half my sims...)

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Repairing your game on Origin is almost the same as reinstalling - and with TS2 it's often best to use it as a last resort. This is most likely a CC issue, and the only thing a reinstall can fix is to reset your game, which is much easier done by removing (or renaming, so you have a backup of your old game - just add "OLD" behind) your "The Sims™ 2 Ultimate Collection" folder, and letting a new folder regenerate. Tadah! New game! It's also a very useful way to test downloads or test if something is wrong with your install or if it's just CC, because this gives you a "blank slate" without actually reinstalling (from whatever is in your install folder, mind - so you don't have to install lights or GraphicRules or all those things every single time something's up with your game).

This may be GUID conflict with skin. The symptoms are same.

Skins usually don't have GUIDs (not like objects, anyway). They do have instances and such. As long as they've been made in Bodyshop they should have separate instance numbers. There are possibly a few exceptions for modded objects with skins or clothes attached to them in some way or another, but as a general rule, CAS items tend not to have GUIDs.

I think the most likely problem is that the texture has the wrong settings, and that somehow this texture is behaving like a default replacement overlay for female skin. Since removing the outfits and some resetting seem to have fixed it, I'm thinking this is what caused the problem, and if it is, it does have a couple fairly simple solutions (not using the outfit, or a text fix in the recolor files).