I have Ren's elf ears 2 and 3, and even after following the blue-flashing-fix tutorial I've found they show up incorrectly in CAS. I have not yet loaded a sim with them into live mode. This is not the only custom content affected - three of the four horns with Marvine's mesh and Enayla's pixie recolour also have this problem. The affected horns are the stubby ones, the satyr ones are fine.

I have many recolours of these ears, but regardless of which one I click they show up stark white with no texture. There is shading in the correct colours, however.

Their thumbnails show up correctly.

Attached is a picture of what it looks like.

I have SimPE so if something is set wrong I can probably fix it if given instructions.

Update: there was also some custom jewelery that was broken in the same way in some angles and not others, and I decided to see if it was broken in live mode and it wasn't.

Still weird that it was broken in CAS, plus that does make it harder to tell if I have the correct ear/skintone matchup (there are over fifty of them).

Looks like the "bright CAS items" bug - I have the same issue with some of the other elf ears, but it happens with other items as well (both default and CC - I have a few random hairs, outfits and accessories). From pictures I've seen, it appears some people also get random bright furniture in CAS with this bug (I don't have this). The elf ears should look fine on lots, though (after a bit of TXMT fixing*). The items I have issues with look fine in live mode and in Bodyshop.

It's not entirely certain what causes this bug, but one fix could be the DXVK, found here: https://modthesims.info/showthread.php?t=633003
(This fix does have some potential issues - it seems to cause random crashes for me and a few other people, which it was supposed to help stop. I've removed it for now - but it's not certain it will have that problem for you - some people report it's working very well for them. Also, I think there's been at least one update since the version I installed. At the moment I'm trying a few other options before deciding if I want to go back to the DXVK).

(* I think all the elf ears with the original mesh/recolor bases by that creator appear to be "broken" by the "bright bug" - they also have a few other issues in the TXMT resource, which never were fixed, so even when they don't have the "bright" bug, they'll look like they've turned inside out, and they'll also be darker than the skintone used for the texture. I needed a couple recolors of some other ears by that creator, which made me poke into the files a bit, and there were several issues I had to fix for them to appear properly in live mode. Couldn't find anything that caused the bright bug, though - still looking for an answer to that one, but I don't think the main answer for it is in the files).