Skin overlay works in CAS but disappears in Live Mode for specific Sims

I have a issue with a default skin overlay (Tinsel by Lamatisse). It has been working perfectly for over a year, but a few days ago it randomly broke for only TWO Sims in my household.
Here is the exact problem:
I have a family of 4 Sims: 2 Young Adults and 2 Adults. The 2 Young Adults (and all sims in the world) look completely fine and have the Tinsel default skin. However, the 2 Adults randomly lost it and went back to the standard EA skin.
In CAS, the default skin shows up perfectly on them. But the moment I return to Live Mode, it completely disappears and they go back to the EA skin.
What I’ve already tried (and didn't work):

• Checked graphics settings (Laptop Mode is OFF, Sim Quality is set to Ultra).
• Re-downloaded and replaced the skin file with a fresh one.
• Repaired the game through EA App and deleted localthumbcache.package + all other cache files.
• Reset the Sims via cheats.
• Changed their clothes/outfits.
• Aged them down to Young Adult in CAS and aged them back up (using cas.fulleditmode).
• They are regular human Sims (not occults), they don't have sunburns, medical wearables, or tattoos.
• I don't have any other default skin files in my Mods folder.
• Moved all my other mods to the desktop and left only the Tinsel skin in the Mods folder to test it.

any ideas on how to fix this? Thanks!