Ideas
I have had this issue for months now. I use mods and cc but this issue persists even with all my mods and cc completely taken out of my game. For context, I play on my laptop and the game runs well other than this consistent glitch.
Essentially, Sims age up from infants with a constant smell cloud like they have a dirty diaper that remains even until they're elders, they fold into an infant pose and wiggle like the infants randomly every so often, and they get infant quirks, notifications and moodlets (and sometimes toddler moodlets and notifications too) in every subsequent life stage.
I have noticed that this glitch only happens when an infant is aged up with a dirty diaper, otherwise the infant ages up fine and has none of these weird glitches the rest of their life.
It is very annoying, especially as I am playing the 100 baby challenge so I constantly have infants aging up. It ruins photos of the Sims because the smell cloud is always visible! And the notifications are so often that I have to clear my notification wall really frequently. Also, the Sims get uncomfortable, sad or angry moodlets from infant-related/toddler-related moodlets that are obviously not relevant, like being gassy or not wanting to wake up etc.
All of the below screenshots were taken within a 10 minute timeframe - this demonstrates how persistent and obvious this issue is!
Please look into this and fix it! Thank you