Ideas
I also get this too. What happens for me is that when NPC Toddlers arrived at the Playground for the first time they stretch as soon as they arrive. It happened when I was testing the new lot in a completely clean unmodded folder in a new save while testing for my bugs. I was trying to find hidden features in the playground lot before I go back to modded. I did do a clean folder for sims 4 by taking the old one out and repair my game to see if any issues pop up. This issue popped up for me in a modded save but after I did all this and moved the entire sims 4 folder to the hard drive and repaired the game and it still popped up. Hope this helps and no none of my sims inventories didn't go missing in my test. I did test that too. It's unknown why this happens to me so I posted it here since it's unknown. I do want to add is that when they show up again. They don't stretch again. This is to me unknown what is going on. I will create a thread to see if anyone has the issue of this when toddlers arrive to lots stretching since this could be own thread worthy. Edit= I created my own here about this. https://forums.ea.com/idea/the-sims-4-bug-reports-en/npc-toddlers-stretch-when-visiting-playground-lots-for-the-first-time-/12623350