Sims UI Broken

I have performed several tests on a clean game (Mods folder removed, game and EA app caches cleared). Here is exactly what I observed:

1. New Sim behavior: A new Sim created from scratch works fine when first loaded. However, if I return to the Main Menu and reload that same Sim, the issues appear.
2. Genetic Twin test: When I create a genetic twin of a Sim from a session where the bug occurred, the twin shows the same issues immediately. This happens even if I save that twin to the library and place them in a completely new save file.
3. UI behavior (Stage 1): Upon loading, some icons are grey squares. The Career panel either shows hashtags (like Time: #...) or does not open at all.
4. UI behavior (Stage 2): If I enter Build Mode or CAS and then return to Live Mode, the UI disappears completely.
5. Cross-Save Contamination: I observed that if I start in a 'corrupted' save (Stage 1), go back to the Main Menu, enter CAS to browse some Sims, and then load a previously healthy save, that save immediately jumps to Stage 2 (total UI disappearance). The error travels from one save to another through the game's active memory.
6. Current state: When the UI is gone, I can still move the camera and the simulation continues, but I have to use Task Manager to kill the process to exit the game.

I have a video recording of this exact sequence: loading a broken save, returning to the menu/CAS, and then loading a healthy save which then becomes broken. If it helps, I can provide a link to this footage for your technical team.