[FIXED] No persistent hairstyle and facial hair CAS thumbnails

Product: The Sims 4
Platform:PC
Which language are you playing the game in? English
How often does the bug occur? Every time (100%)
What is your current game version number? 1.80.69.1030
What expansions, game packs, and stuff packs do you have installed? All packs
Steps: How can we find the bug ourselves? 1) In the default Windows folder "Documents", go in the folder "Electronic Arts" and then "The Sims 4". There should be a file called "localthumbcache.package". Delete this file. 2) Launch the game, and enter Create-a-Sim by any possible mean. 3) Start creating a young adult Sim with a Feminine body frame and Feminine clothing preference. 4) Scroll through the hair category until you reach items included in content packs released before Dream Home Decorator (DHD). You should notice many CAS items with initially no thumbnail. Wait until the game generate thumbnails for all visible items. 5) Scroll around in the hair category until you see more CAS items with no thumbnail. You should notice many CAS items with initially no thumbnail. Wait until the game generate thumbnails for all visible items. 6) Untick the "Feminine" filter then scroll around to find more CAS items with no thumbnails from content packs from packs released earlier than DHD. These should correspond to non-Feminine (mostly Masculine) hair items, which should eventually get a thumbnail with a Sim with Feminine body frame. Repeat step 5 until thumbnails for all hair items have been generated. 7) **Optional** Repeat steps 3–6 with all age stages up to young adult (i.e. toddler/child/teen/young adult), all possible body frames (Feminine/Masculine), all possible clothing preferences (Feminine/Masculine) and with facial hair (when applicable). When repeating step 6, untick the filter which corresponds to that clothing preference. 8) Close the game. 9) Repeat steps 1–6 (and step 7 if you have time). You should notice that all hairstyles and facial hairs from packs released earlier than DHD no longer have a thumbnail and that the game tries to generate new thumbnails again.
What happens when the bug occurs? Hairstyles and facial hair from packs released earlier than DHD do not initially have a thumbnail. They appear with a blank white image, and a proper thumbnail is generated as the player scrolls through hairstyles and facial hairs. CAS thumbnails are slowly generated one after the other, with items currently visible in the CAS interface getting a thumbnail first. Additionally, thumbnails of Feminine (resp. Masculine) hairstyles with Masculine (Feminine) body frames are only generated when the player browse through the hairstyle category, unticks the Feminine (Masculine) outfit preference and scrolls through all available hairstyles.
What do you expect to see? I expected thumbnails to remain in place no matter when the "localthumbcache.package" file is deleted, just like with other packs.
Have you installed any customization with the game, e.g. Custom Content or Mods? Not now. I've removed them.
Did this issue appear after a specific patch or change you made to your system? Yes
Please describe the patch or change you made. Patch 1.75.125.1030 for PC

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Bug appeared with patch 1.75.125.1030 for PC, which added new hair colors to the game. All hairstyles and facial hairs should have received new thumbnails using the new, blackest hair colour (instead of the colour used before), but it doesn't appear to be the case. Unfortunately, hairstyles and facial hairs from content packs released prior DHD apparently have no such thumbnail, and the game tries to generate new ones every time the "localthumbcache.package" file is deleted for any reason (re-installing the game, deleting it for bug testing or when installing new mods...). Here's a video example.

The base game and content packs released from DHD onward (aka DHD and CoL at the time of writing) are unaffected. Hairstyles added to the base game since patch 1.75.125.1030 are unaffected.

All age stages and all combinations of body frame and outfit preferences (Feminine/Masculine) are affected. The game tries to generate thumbnails for them only when needed, which means that the player has to scroll through all hairstyles and facial hairs for all ages, all body frames and make sure to try to choose Feminine (resp. Masculine) hairstyles with a Sim with a Masculine (Feminine) body frame for all missing thumbnails to be generated.

A consequence of this bug is that, when attempting to save a household in CAS, if thumbnails of CAS items are not done being generated, this will delay households thumbnails from being generated (because CAS items apparently take priority over household thumbnails). In turn, this prevents the player from saving their household until CAS items and thence household thumbnails are all generated. With a lot of packs installed and a high-range computer, this can prevent players from saving their household for 1–2 minutes.

This bug also overlaps with a similar bug with all CAS items from Holiday Celebration Pack.

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